Prosthetic heart valve and endoprosthesis comprising a prosthetic heart valve and a stent

ABSTRACT

The invention relates to a prosthetic heart valve ( 100 ) for an endoprosthesis ( 1 ) used in the treatment of a stenotic cardiac valve and/or a cardiac valve insufficiency. The prosthetic heart valve ( 100 ) comprises of a plurality of leaflets ( 102 ), which consist of a natural and/or synthetic material and have a first opened position for opening the heart chamber and a second closed position for closing the heart chamber, the leaflets ( 102 ) being able to switch between their first and second position in response to the blood flow through the heart. In addition, the prosthetic heart valve ( 100 ) comprises a leaflet support portion ( 103 ), consisting of biological and/or synthetic material for mounting of the prosthetic heart valve ( 100 ) to a stent ( 10 ), and a bendable transition area ( 104 ) which forms a junction between the leaflets ( 102 ) and the leaflet support portion ( 103 ), the transition area ( 104 ) progressing essentially in a U-shaped manner similar to a cusp shape of a natural aortic or pulmonary heart valve for reducing tissue stresses during opening and closing motion of the leaflets ( 102 ). The invention further relates to an endoprosthesis ( 1 ) comprising a prosthetic heart valve ( 100 ) and a stent ( 10 )

This application claims priority to U.S. Provisional Application No.61/348,036 filed May 25, 2010 and to EP Application No. 10163831.0 filedMay 25, 2011, the entire disclosures of each of which are incorporatedherein by reference.

The present disclosure relates to a prosthetic heart valve.Specifically, the present disclosure relates to a prosthetic heart valvefor a transcatheter delivered endoprosthesis used in the treatment of astenotic cardiac valve and/or a cardiac valve insufficiency.

The present disclosure also relates to a transcatheter deliveredendoprosthesis that includes a prosthetic heart valve and a stent forpositioning and anchoring of the prosthetic heart valve at theimplantation site in the heart of a patient. Specifically, the presentdisclosure also relates to a collapsible and expandable prosthesisincorporating a prosthetic heart valve and a stent that can be deliveredto the implant site using a catheter for treatment of a stenosis(narrowing) of a cardiac valve and/or a cardiac valve insufficiency.

The expression “narrowing (stenosis) of a cardiac valve and/or cardiacvalve insufficiency” may include a functional defect of one or morecardiac valves, which is either genetic or has developed. A cardiacdefect of this type might affect each of the four heart valves, althoughthe aortic and mitral valves are affected much more often than theright-sided part of the heart (pulmonary and tricuspid valves). Thefunctional defect can result in narrowing (stenosis), inability to close(insufficiency) or a combination of the two (combined vitium). Thisdisclosure relates to a prosthetic heart valve as well as atranscatheter delivered endoprosthesis that includes a prosthetic heartvalve and an expandable stent capable of being implanted transluminallyin a patient's body and enlarged radially after being introduced bytranscatheter delivery for treating such a heart valve defect.

The human heart has four valves which control the blood flow circulatingthrough the human body. On the left side of the heart are the mitralvalve, located between the left atrium and the left ventricle, and theaortic valve, located between the left ventricle and the aorta. Both ofthese valves direct the oxygenated blood, coming from the lungs into theaorta for distribution through the body. The tricuspid valve, locatedbetween the right atrium and the right ventricle, and the pulmonaryvalve, located between the right ventricle and the pulmonary artery,however, are situated on the right side of the heart and directdeoxygenated blood, coming from the body, to the lungs.

The native heart valves are passive structures that open and close inresponse to differential pressures induced by the pumping motions of theheart. They consist of moveable leaflets designed to open and close inresponse to the said differential pressure. Normally, the mitral valvehas two leaflets and the tricuspid valve has at least two, preferablythree leaflets. The aortic and pulmonary valves, however, have normallyat least two, preferably three leaflets, also often referred to as“cusps” because of their half-moon like appearance. In the presentdisclosure, the terms “leaflet” and “cusps” have the same meaning.

Heart valve diseases are classified into two major categories, namedstenosis and insufficiency. In the case of a stenosis, the native heartvalve does not open properly, whereby insufficiency represents theopposite effect showing deficient closing properties. Medical conditionslike high blood pressure, inflammatory and infectious processes can leadto such cardiac valve dysfunctions. Either way in most cases the nativevalves have to be treated by surgery. In this regard, treatment caneither include reparation of the diseased heart valve with preservationof the patient's own valve or the valve could be replaced by amechanical or biological substitutes also referred to as prostheticheart valves. Particularly for aortic heart valves, however, it isfrequently necessary to introduce a heart valve replacement.

In principle, there are two possibilities of treating the diseased heartvalve, when inserting a prosthetic heart valve: The first way includesextracting at least major parts of the diseased heart valve. The secondalternative way provides leaving the diseased heart valve in place andpressing the diseased leaflets aside to create space for the prostheticheart valve.

Biological or mechanical prosthetic heart valves are typicallysurgically sewn into the cardiac valve bed through an opening in thechest after removal of the diseased cardiac valve. This operationnecessitates the use of a heart-lung machine to maintain the patient'scirculation during the procedure and cardiac arrest is induced duringimplantation of the prosthesis. This is a risky surgical procedure withassociated dangers for the patient, as well as a long post-operativetreatment and recovery phase. Such an operation can often not beconsidered with justifiable risk in the case of polypathic patients.

Minimally-invasive forms of treatment have been developed recently whichare characterized by allowing the procedure to be performed under localanesthesia. One approach provides for the use of a catheter system toimplant a self-expandable stent to which is connected a collapsibleheart valve. Such a self-expandable endoprosthesis can be guided via acatheter system to the implantation site within the heart through aninguinal artery or vein. After reaching the implantation site, the stentwith the prosthetic heart valve affixed thereto can then be unfolded.

An increasing number of patients suffer from stenosis (narrowing) ofcardiac valve and/or cardiac valve insufficiency. In this regard, theissue concerning the provision of long term durability is involved withdeveloping prosthetic heart valves. Each of the four major heart valvesopen and close about 100,000 times a day and stability requirements forreplacements valves are particularly high.

Moreover, there is the danger that—due to the dynamic fluid pressurefrom blood flow through the prosthetic heart valve, the leafletmaterial, or the threads (e.g. sutures) used in fastening the prostheticheart valve to the stent may tear or break. These component failuresover the course of time may result in loss of overall valve function.

On the basis of the problems outlined above and other issues withcurrent transcatheter technologies, certain embodiments of the presentdisclosure address the issue of providing a prosthetic heart valve, aswell as a self-expandable endoprosthesis for treating a narrowed cardiacvalve or a cardiac valve insufficiency which realizes optimum long termdurability, excellent hemodynamics (e.g. low pressure gradients andminimal regurgitation), minimization of paravalvular leakage, accuratedevice alignment and positioning, no coronary obstruction, prevention ofdevice migration and avoidance of heart block. In addition, thedisclosure provides an improved attachment of a prosthetic heart valveto a corresponding collapsible stent structure, thereby distributingstress loads over a greater surface area and thus reducing the potentialfor stress concentration points throughout the prosthetic heart valve,resulting in improved durability.

In this regard and as it will be described later in detail, thedisclosure provides a prosthetic heart valve for a transcatheterdelivered endoprosthesis used in the treatment of a stenosis (narrowing)of a cardiac valve and/or a cardiac valve insufficiency. The prostheticheart valve comprises at least two leaflets, a skirt portion, and atransition area representing a junction between the leaflets and theskirt portion. Each of the at least two leaflets of the prosthetic heartvalve consists of natural tissue or synthetic material and has a firstopened position for opening the patient's heart chamber and a secondclosed position for closing the patient's heart chamber, the at leasttwo leaflets being able to switch between their first and secondposition in response to the blood flow through the patient's heart. Theskirt portion consists of natural tissue or synthetic material and isused for mounting of the prosthetic heart valve to a stent. Thetransition area, which represents a junction between the at least twoleaflets of the prosthetic heart valve and the skirt portion, progressesapproximately in a U-shaped manner, similar to a cusp shape of a naturalaortic or pulmonary heart valve, thereby reducing stresses within theheart valve material during opening and closing motion of the at leasttwo leaflets.

The expression “natural tissue” as used herein means naturally occurringtissue, i.e. biological tissue obtained from the patient, from anotherhuman donor, or from a nonhuman animal. On the other hand, the hereinused expression “natural tissue” shall also cover tissue fabricated bytissue engineering in the laboratory, for example, from combinations ofengineered extracellular matrices (“scaffolds”), cells, and biologicallyactive molecules.

As it will be described in detail later on, in some embodiments of thepresent disclosure, the prosthetic heart valve either comprisesxenografts/homografts or synthetic, nonbiological, non-thrombogenicmaterials. Homografts are either human donor valves, e.g., heart valves,or replacements made of human tissue, e.g., pericardial tissue. Incontrast, xenografts describe valves received from animals, e.g., heartvalves, or made of animal tissue, e.g., pericardial tissue, typicallyporcine or bovine respectively. These natural tissues normally containtissue proteins (i.e., collagen and elastin) acting as a supportiveframework and determining the pliability and firmness of the tissue.

It is conceivable to increase the stability of said natural tissues byapplying chemical fixation. That is, the natural tissue may be exposedto one or more chemical fixatives (i.e. tanning agents) that formcross-linkages between the polypeptide chains within the proteinstructures of the natural tissue material. Examples of these chemicalfixative agents include: formalaldehyde, glutaraldehyde, dialdehydestarch, hexamethylene diisocyanate and certain polyepoxy compounds.

So far, a major problem with the implantation of conventional biologicalprosthetic heart valves is that the natural tissue material can becomecalcified, resulting in undesirable stiffening or degradation of theprosthetic heart valve.

Even without calcification, high valve stresses can lead to mechanicalfailure of components of the heart valve. In order to overcome problemswith mechanical failure and potential stress induced calcification thatlimit valve durability, some embodiments of the disclosure describe animproved construction of the prosthetic heart valve, the design of thedisclosed prosthetic heart valve is suited for reducing stresses, andreducing the potential for calcification to improve durability of theheart valve.

In addition, the disclosure provides an improved attachment of aprosthetic heart valve to a corresponding collapsible stent structure,thereby distributing stress loads over a greater surface area and thusreducing the potential for stress concentration points throughout theprosthetic heart valve, resulting in improved durability.

In some embodiment of the disclosure, the prosthetic heart valve may bemade of one piece of flat pericardial tissue. This pericardial tissuecan either be extracted from an animal's heart (xenograft) or a human'sheart (homograft). Subsequently, the extracted tissue may be cut by alaser cutting system, a die press, a water jet cutting system or by handwith a variety of cutting instruments in order to form a patternrepresenting each of the at least two leaflets or in another embodimentindividual leaflets. This pattern may also include the skirt portion insome embodiments. The skirt portion represents an area of the prostheticheart valve that is used for connecting the prosthetic heart valve to astent, for example, by means of sutures. Current prosthetic heart valvesconsist of separated leaflets and skirt portions, wherein the separatedleaflets and skirt portions are sewn together by the time the biologicalheart valve is connected to the stent. According to the “one piece”embodiment described herein, however, the leaflets are integrally formedwith the leaflet support portion, that is the prosthetic heart valve ismade of one piece of flat pericardial tissue.

The pattern of the prosthetic heart valve, which represents each of theat least two and preferably three leaflets and the skirt portion, shallsubstantially be constructed like a native aortic or pulmonary heartvalve. To this end, the pattern is preferably designed so as to formleaflets in the aforementioned cusp manner, having three half-moonshaped leaflets like the aortic or pulmonary heart valve. The leafletscan be designed in various shapes such as the geometry of an ellipse,U-shape or substantially oval. In this regard, preferably each of thethree different leaflets is formed in such a manner that all of themhave the same extent; however, it is also conceivable to design them indifferent sizes.

The shaping of the leaflets into said pattern, for minimizing stressesin the closed position of the prosthetic heart valve, can be achieved inseveral ways. Most importantly, the mechanical properties of theleaflets of the prosthetic heart valve are influenced by the free marginand the shape of the supported edges. To this end, in an advantageousembodiment disclosed herein, the leaflets are formed into apredetermined 3D shape, by means of a cross-linking the flat tissue on amandrel. Subsequently, potentially occurring excess material is trimmedoff by means of a laser, knife, or water jet respectively to form theedges of the 3D shape. Between the leaflets and the skirt portion, thevalve pattern shows a transition area progressing in a substantialU-shaped manner, similar to the cusp shape of a natural aortic orpulmonary heart valve.

In another embodiment of the present disclosure, the lower end sectionof the prosthetic heart valve exhibits a tapered or flared shape. Such atapered or flared shape may be advantageous regarding the attachment ofthe prosthetic heart valve to a corresponding stent. As will beexplained in more detail hereinafter, a corresponding stent may comprisea tapered or flared lower end section in order to improve the anchoringof the stent at the implantation site. As a consequence, it may beuseful to construct the lower end section of the prosthetic heart valvein a tapered or flared shape, so as to prevent paravalvular leakagebetween the stent and the blood vessel.

According to another embodiment of the present disclosure, the leafletsmay have a cuspidal geometry, which is formed in an elliptically,u-shaped or oval manner. Such a cuspdial geometry reduces the potentialfor stress concentrations and therefore minimizes the potential forareas of wear and calcium deposition. In another embodiment of thepresent disclosure all three leaflets are shaped to the same extent,absorbing loads equally throughout the cardiac cycle. However, it isconceivable to assemble a device with leaflets of varying designs.

With reference to another embodiment of the present disclosure, theleaflet portion of the prosthetic heart valve is designed to provideredundant coaptation for potential annular distortion. In particular,redundant coaptation means that each of the leaflets covers more thanone third of the inner diameter of the respective stent, in the closedposition of the valve. The redundant coaptation may reduce stress on theleaflets and provides reliable closure of the heart chamber in thesecond closed position of the leaflets, even in the case of an annulardistortion. That is, the prosthetic heart valve of the presentdisclosure is capable of preventing regurgitation even if the size ofthe heart valve annulus has been altered (annular distortion).

In another embodiment of the present disclosure, the prosthetic heartvalve comprises a plurality of fastening holes provided along theprogression of the bendable transition area. These fastening holes arepreferably introduced into the tissue of the prosthetic heart valvebefore the valve is attached to the corresponding stent. This pluralityof fastening holes may reduce the time needed for attachment of theprosthetic heart valve to the retaining arches of the correspondingstent.

According to another aspect of the present disclosure, the prostheticheart valve is designed for collapsing and delivering in a catheter. Tothis end, the prosthetic heart valve can be designed in such a way as tofit inside the corresponding stent structure. Furthermore, it isconceivable that the design of the prosthetic heart valve comprisescertain folds in order to allow for collapsing to very small diameters.

In another embodiment of the invention, the tissue material of theprosthetic heart valve has a thickness of 160 μm to 300 μm, preferablyfrom 220 μm to 260 μm. However, it should be noted that the thicknessmay be dependent on the tissue material of the prosthetic heart valve.In general, the thickness of bovine tissue is thicker than the thicknessof porcine tissue.

The blood vessels and heart valve orifices of the individual patientscan have significantly varying diameter, accordingly, the prostheticheart valve may have a diameter ranging form 19 mm to 28 mm. Thus, theprosthetic heart valve of the present disclosure is adapted to fit tothe individual characteristics of individual patient's heart anatomy.

In another embodiment of the present disclosure, the bendable transitionarea of the prosthetic heart valve is attached to retaining arches ofthe stent by means of sutures, having a diameter larger than thediameter of the sutures used for attachment of the prosthetic heartvalve to an annular collar of the stent. Due to this, the prostheticheart valve can be reliably attached to the stent without adding toomuch bulk to the stent, in order to collapse the endoprosthesis to asmall diameter.

The disclosure also provides a transcatheter delivered endoprosthesishaving a prosthetic heart valve affixed to a stent. The stent providesretaining arches which are configured once in the expanded state to bein a gradually uniform U-shape. The transition area of the tissue isattached to the retaining arches of the stent in a number of possibleembodiments. The purpose of the retaining arches is to control themotion of the leaflets during the opening and closing phases of thevalve in a manner which minimizes the stresses associated with thecyclic motion.

In general, current transcatheter prosthetic heart valves consist ofseparated leaflets and skirt portions, wherein the separated leafletsand skirt portions are sewn together by the time the biological heartvalve is connected to the stent. Hence, with the conventional prostheticheart valves, additional suture lines are necessary, causing stressconcentration and reduced flexibility of the heart valve, thus leadingto earlier calcification of the prosthetic heart valves.

In order to reduce or minimize stress concentration and to enhanceflexibility of the heart valve, in some embodiments as disclosed hereinthe leaflets are integrally formed with the skirt portion. For example,a single piece of pericardium may be used for forming the prostheticheart valve. As an alternative, the skirt portion may consist ofmultiple pieces of tissue, e.g. three pieces of tissue, which are sewntogether by the time the biological heart valve is connected to thestent, wherein the leaflets are integrally formed with the tissuematerial of the pieces which together form the skirt portion. Forexample, three individual tissue panels may be utilized to construct thevalve portion of the prosthetic heart valve. Whether a single piece ofpericardium or three panels are used, the tissue structure is sutured tothe stent structure to create the desired U-shape of the leaflets. ThisU-shape helps distribute the load on the leaflets throughout the cardiaccycle, but especially when in the closed position.

By avoiding that the leaflets must be sewn to the skirt portion(s),greater strength and durability of the heart valve assembly may beprovided, as the strength and integrity of a uniform piece of tissue isimproved from separate pieces of tissue sewn together. Additionally, theadvantages of not having a seam include reduced assembly time (lesssuturing), less overall bulk when collapsing the prosthesis for smallcatheter delivery and more flexible leaflets at the transition area thatcould improve leaflet motion and hemodynamics.

The natural tissue material used for the manufacture of prosthetic heartvalves typically contains connective tissue proteins (i.e., collagen andelastin) that act as supportive framework of the tissue material. Inorder to strengthen this compound of tissue proteins, a chemicalfixation process may be performed, linking the proteins together. Thistechnique usually involves the exposure of the natural tissue materialto one or more chemical fixatives that form the cross-linkages betweenthe polypeptide chains of the collagen molecules. In this regard, it isconceivable to apply different cross-linking techniques for differentparts of the prosthetic heart valve tissue. For instance, the leafletsof the prosthetic heart valve could be treated by a different chemicalfixative agent than the skirt portion in order to obtain diverserigidity within the prosthetic heart valve.

In addition, it is conceivable to have leaflets and a skirt which arenot integral. In this case, different cross-linking techniques may beapplied to the leaflets and the skirt.

Examples of chemical fixative agents conceivably used for cross-linkingof the prosthetic heart valve, according to the present disclosureinclude: aldehydes, (e.g. formaldehyde, glutaraldehyde, dialdehydestarch, para formaldehyde, glyceroaldehyde, glyoxal acetaldehyde,acrolein), diisocyanates (e.g., hexamethylene diisocyanate),carbodiimides, photooxidation, and certain polyepoxy compounds (e.g.,Denacol-810,-512).

According to some of the disclosed embodiments, the prosthetic heartvalve is mounted to the inner surface of a support stent. Thisarrangement facilitates protection of the prosthetic heart valvematerial during collapse and deployment. This is because the prostheticheart valve is not in contact with the inner wall of the implantationcatheter, and thus may not get stuck on the inner surface thereof. Onthis account, damage to the prosthetic heart valve is avoided. Also,such an endoprosthesis can be collapsed to a smaller diameter comparedwith a prosthetic heart valve mounted to the outer surface of the stent,hence providing the possibility to use smaller catheters.

On the other hand, it is conceivable to mount the prosthetic heart valveto the outer surface of a support stent. That is, the skirt portioncould be in direct contact with the diseased native heart valve andcould be attached to the stent by means of sutures. Mounting theprosthetic heart valve to the outer surface of the stent supports theload transfer from the leaflet to the stent. This greatly reducesstresses on the leaflets during closing and consequently improves thedurability thereof. Also, it is possible to design the valve to obtainimproved hemodynamics in the case of mounting the skirt portion andcommissures to the outer surface of the stent. Additionally, the heartvalve material which is in direct contact with the diseased native heartvalve provides a good interface for sealing against leakage (i.e.,paravalvular leakage), tissue in-growth and attachment. The stentdesigns for this endoprosthesis uniquely accommodate this valveembodiment and advantages, whereas for cage-like transcatheter deliveredstent designs this is not possible.

The prosthetic heart valve can be made from pericardial tissue, forexample, human pericardial tissue, preferably animal pericardial tissue,whereby bovine or porcine pericardial tissue is preferred. However, itis conceivable to employ kangaroo, ostrich, whale or any other suitablexeno- or homograft tissue of any feasible dimension.

Preferably, porcine tissue thicknesses of 220 to 260 μm after fixationshall be used to manufacture the biological prosthetic heart valves. Ofcourse, this example is not a limitation of the possible kinds oftissues and their dimensions. Rather, it is conceivable to employkangaroo, ostrich, whale or any other suitable xeno- or homograft tissueof any feasible dimension.

Many aspects of the disclosed prosthetic heart valve embodiments maybecome clear considering the structure of a corresponding stent to whichthe prosthetic heart valve may be attached in order to form atranscatheter delivered endoprosthesis used in the treatment of astenosis (narrowing) of a cardiac valve and/or a cardiac valveinsufficiency.

According to an aspect of the disclosure, a stent suitable forimplantation with the aforementioned prosthetic heart valve may comprisepositioning arches configured to be positioned within the pockets of thepatient's native heart valve. Furthermore, the stent may compriseretaining arches. In detail, for each positioning arch one retainingarch may be provided. In the implanted state of the stent, therespective head portions of the positioning arches are positioned withinthe pockets of the patient's native heart valve such that thepositioning arches are located on a first side of a plurality of nativeheart valve leaflets. On the other hand, in the implanted state of thestent, the retaining arches of the stent are located on a second side ofthe native heart valve leaflets opposite the first side. In thisrespect, the positioning arches on the one hand and the retaining archeson the other hand clamp the native heart valve leaflets in a paper-clipmanner.

Hence, the positioning arches of the stent are designed to engage in thepockets of the native (diseased) cardiac valve which allows accuratepositioning of the stent and a prosthetic heart valve affixed to thestent. Furthermore, in the implanted state, each positioning archco-operates with a corresponding retaining arch resulting in clipping ofthe native leaflet between the two arches. In this way, the positioningand retaining arches hold the stent in position and substantiallyeliminate axial rotation of the stent

In a preferred embodiment, the positioning arch may be formed such as tohave a substantially convex shape. In this way, the shape of eachpositioning arch provides an additional clipping force against thenative valve leaflet.

The at least one retaining arch of the stent may be connected to acorresponding positioning arch by a connecting web. The retaining archmay extend substantially parallel to the positioning arch, thus havingessentially the same shape. The shape of the retaining arch basicallyrepresents a U-shape with a small gap at its lower end. This gap issurrounded by a connection portion which originates during thefabrication of the tip of the positioning arches. The connection portionmay be similar to a U- or V-shape and links the two sides of a retainingarch.

Along the retaining arches of the stent, a plurality of fastening holesand optionally one or more notches may be provided. Preferably, thesefastening holes and notches are longitudinally distributed at givenpositions along the retaining arches and guide at least one thread orthin wire to fasten the tissue components of the prosthetic heart valveto the stent, thereby enabling a precise positioning of the tissuecomponents on the stent. The means provided for fastening the tissuecomponents of the biological prosthetic heart valve to the retainingarches of the stent (thread or thin wire) is guided by way of thefastening holes and notches to ensure accurate repeatable securement ofthe bioprosthetic heart valve within the stent structure. This accuratesecurement of the biological prosthesis substantially reduces thepotential for longitudinal displacement of the biological prostheticheart valve relative to the stent.

According to another embodiment of the present disclosure, theaforementioned plurality of retaining arches are provided with one ormore fastening notches which can be used to fix the bendable transitionarea to the stent. To this end, the retaining arches may be segmented bya plurality of bending edges forming said fastening notches and definingbending points of the retaining arches. The fastening notches simplifythe attachment of the bendable transition area of the prosthetic heartvalve to the retaining arches.

In another aspect of the stent which is suitable for implantation with abiological prosthetic heart valve as disclosed herein, the retainingarches are cut from the material portion of a small metal tube in anshape that when expanded essentially form the U-shaped structurecorresponding to the aforementioned progression of the transition area.

At the lower end of the stent, an annular collar may be provided. Theannular collar may serve as a supporting body through which the radialforces, developing due to the self-expansion, are transmitted to thevascular wall. Attached to the annular collar is the skirt portion ofthe biological prosthetic heart valve. Typically, this attachment isimplemented by means of suturing.

The intent of the self expanding annular collar in combination with theattached skirt region of the valve is to provide sufficient radialforces so as to seal and prevent paravalvular leakage. In addition, thecollar aids in anchoring the prosthesis in the annulus to preventmigration. This collar may incorporate a flared or tapered structure tofurther enhance securement.

As mentioned above, a prosthetic heart valve can be attached to acorresponding stent in order to provide a transcatheter deliveredendoprosthesis which can be used in the treatment of a stenosis(narrowing) of a cardiac valve and/or a cardiac valve insufficiency.

A prosthetic heart valve made from pericardial tissue material may beattached to the retaining arches and annular collar of theafore-mentioned stent by means of braided multi-filament polyestersutures. These sutures may have any suitable diameter, typically about0.07 mm.

In order to increase the strength of the connection of biologicalprosthetic heart valve to the stent, however, it is conceivable toincrease the size of the multi-filament sutures, for example, up to 0.2mm. In this way, it is possible that the fundamental bond between thetransition area of the prosthetic heart valve and the retaining archesof the stent exhibits additional stability. On the other hand, theremaining sutures shall be kept as thin as possible to enable collapsingof the endoprosthesis to a small diameter.

A common running stitch pattern may be used to obtain said bonding.According to the disclosure, the stitch pattern is preferably a lockingstitch or a blanket stitch respectively. Of course, any other suitablestitch pattern (i.e. overlocking stitch, slipstitch or topstitch) isalso possible.

Considering the stress concentration due to direct stitching in theheart valve material, another aspect of the disclosure may provide thatthe material of the prosthetic heart valve is reinforced to improve itssuture retention force. To this end, laser cut suturing holes may beintroduced into the prosthetic heart valve tissue with the laser cuttingprocess strengthening the tissue area around the cut hole. Predefinedlaser cutting holes might also ease the suturing process itself andreduce stresses on the material of the prosthetic heart valve due to thepenetration of the needle during stitching.

In another embodiment of the present disclosure, the connection of theprosthetic heart valve material to a stent may be reinforced by means ofreinforcement elements. Such reinforcement elements are intended toreduce stress concentrations in the material of the prosthetic heartvalve that may occur from direct stitching in the valve material. Inparticular, the reinforcement elements might reduce stress concentrationin the tissue material of the prosthetic heart valve at the connectionbetween the bendable transition area and the retaining arches of thestent. The reinforcement elements may be placed between an inner sutureand the prosthetic heart valve material, thus distributingaforementioned stresses, caused by the stitching, over a larger area ofthe valve material. These reinforcement elements can be used at discretelocations or continuously along the path of the stitching. For example,they can be placed opposite to the retaining arches of the stent on theother side of the prosthetic heart valve material.

Reinforcement elements may be applied in order to avoid direct contactbetween knots of the sutures and the tissue of the prosthetic heartvalve, thereby reducing abrasion of the prosthetic heart valve tissuedue to rubbing against said sutures. To reduce direct contact betweenthe heart valve tissue and the stent structure or any other metalliccomponent of the endoprosthesis, reinforcement elements can further beused to prevent the tissue of the prosthetic heart valve from directlycontacting the stent structure or any other metallic componentrespectively.

In this regard, it is also conceivable to locate reinforcement elementsalong the entire surface of the prosthetic heart valve. Preferably, suchreinforcement elements could also be located at or near the upper edgeof the leaflets. These upper edges, building the commissures of theendoprosthesis, are exposed to an increased tension, which are morelikely to tear during the operation of the prosthetic heart valve.

Moreover, it is also feasible to place said reinforcement elementsinside the tissue of the prosthetic heart valve, instead of a mereattachment on the surface of the prosthetic heart valve. In this regard,it may be advantageous to have a layer of tissue or synthetic materialof different mechanical properties inside the aforementioned prostheticheart valve. This alternative embodiment may be especially useful inorder to reinforce the leaflets of the prosthetic heart valve in orderto increase their ability to yield mechanical stresses occurring duringthe operation of the endoprosthesis.

Reinforcement elements can be used at discrete locations or continuouslyalong the path of the stitching. For example, they can be placedopposite to the retaining arches of the stent on the other side of theprosthetic heart valve material.

The reinforcement elements may be folded or formed in such a way thatround edges are formed. These round edges are designed to reduce oravoid abrasion of the valve material during opening and closing of theprosthetic heart valve.

With regard to a further embodiment of the present disclosure, thereinforcement elements comprise at least one inner cushion, which ismounted to the inner surface of the bendable transition area of theprosthetic heart valve. This inner cushion is arranged essentiallyopposite the retaining arches and/or to the commissure attachment regionof the stent. Opposite in this context means that the inner cushion ismounted on an opposite side of the prosthetic heart valve. The innercushion is designed to reduce the stress concentrations in the tissuethat occur from direct stitching in the tissue. In more detail, theinner cushion prevents the prosthetic heart valve tissue from directlycontacting knots of the suture. Due to this, wear of the heart valvetissue is reduced, as said knots do not rub on the surface of thetissue, during opening and closing of the heart valve.

In a further embodiment, the at least one inner cushion may be a pledgetmade of one or multiple layer materials. The inner cushion may consistof materials, for examples, like polyester velour, PTFE, pericardialtissue or any other material suitable for forming round edges,distributing or buffering stresses in the valve material, due to thesutures. On this account, the material of the inner cushion can be madefrom flat sheets or fabrics such as knits or woven constructions. It isto be noted that the reinforcement elements can be applied in order tospan between stent struts, in particular across a gap, located at thelower end of the retaining arches, to help support the valve materialacross said gap.

In an alternative implementation, the reinforcement elements may consistof a wire rail placed at the inner surface of the bendable transitionarea of the prosthetic heart valve, essentially opposite the retainingarch of the stent. The wire rail may be secured in place using a stitchpattern meant to accommodate the wire rail and the valve material to thestent. In comparison to the inner cushion mentioned above, such a wirerail could be easier to attach to the material of the prosthetic heartvalve. Furthermore the already rounded shape of the rail does notrequire the wire rail to be folded in order to obtain rounded edges forprevention of valve material abrasion.

It is preferable that said wire rail is made of Nitinol in order toallow collapsing of the reinforcement element simultaneously with thestent structure.

Moreover, in another realisation, the reinforcement elements may beessentially of the same size and form as the retaining arches of thestent, hence forming an inner attachment rail. The reinforcementelements, however, shall be of thinner material than the retainingarches. This is due to the fact that thick material may limit theability of the endoprosthesis to be collapsed to a small size.

In particular, the inner attachment rail may have the same fasteningholes and notches longitudinally distributed at given locations as theretaining arches of the stent. Again, the attachment rail may be placedon the inner surface of the bendable transition area of the prostheticheart valve, opposite to the retaining arches of the stent. Thus, thematerial of the prosthetic heart valve may be clamped in between thestent and the reinforcement element, which are connected throughsutures. The reinforcement element thus may act as an inner attachmentrail for the leaflets of the prosthetic heart valve to bend over andevenly distribute stress loads affecting the valve material over a largeattachment rail rather than individual suture points.

Although most embodiments of the disclosure use sutures to fix thereinforcement element or valve material to the stent, it is conceivableto use different attachment methods like welding, soldering, lockingfixture and rivets. For instance, these methods could be used to attachthe aforementioned inner attachment rail to the retaining arches of thestent. This would result in clamping the prosthetic heart valve materialin between the inner surface of the stent and the outer surface of thereinforcement element without penetrating the valve material withneedles of suture.

Another alternative attachment concept includes a reinforcing elementattached to the back side of the prosthetic heart valve material. Thisconcept may be suitable for attachment in a high stress area of acommissure attachment region on top of the retaining arches, which isdescribed in more detail below. This concept involves creating astrengthened region by folding the prosthetic heart valve material andwrapping it with the reinforcing element. Thus, the reinforcementelement forms an outer wrapping element which is mounted to the outersurface of the bendable transition area of the prosthetic heart valve,at the commissure attachment region of the stent. The reinforcedbendable transition area of the prosthetic heart valve can then besecurely attached to the retaining arches of the stent or the commissureattachment region of the stent.

The aforementioned outer wrapping element of the reinforcing element ispreferably made of a polymer material such as PTFE or a PET fabric orsheet. However, it could also be a more rigid U-shaped clip or bendablematerial that can pinch the folded valve material. One advantage thisconcept has over the other reinforcing elements is that the reinforcingmaterial is not placed on the inner surface of the prosthetic heartvalve, hence does not disrupt the blood flow or potentially be a sitefor thrombus formation.

The outer wrapping element of the reinforcing element may also providean opening buffer to keep the valve leaflet material from opening toowide and hitting the stent, which would cause wear of the valvematerial. Similar to the rounded edges of the other reinforcementelements, these buffers should be rounded, smooth or soft to avoid wearwhen the open valve material hits them. The buffer should be smallenough to not significantly over restrict leaflet material opening.

An especially beneficial embodiment of the present invention includes anattachment concept with reinforcement elements attached to the innersurface and to the outer surface of the transition area of theprosthetic heart valve. This configuration optimally prevents stressconcentration and resulting wear of the prosthetic heart valve.

In particular, a first reinforcement element is connected to the outersurface of the bendable area of the prosthetic heart valve, preferablylining the retaining arches and the commissure attachment region overtheir entire length. The said reinforcement element, which is connectedto the outer surface of the prosthetic heart valve, can be made ofanimal pericardial tissue, such as the one used for the prosthetic heartvalve itself. Of course, it is conceivable to use any other suitablematerial for the reinforcement element, such as synthetic materials oreven homograft (human) tissue. The reinforcement element, connected tothe outer surface of the prosthetic heart valve, has several advantages,such as preventing any rubbing and wear between the leaflet and thestent at the retaining arches or commissure attachment regionrespectively. Even if the attachment is tightly sutured, the tissue willhave strain cycles at the surface during opening and closing motion ofthe leaflets, which can cause wear against the stent from micromovements. Furthermore, the reinforcement element allows for anadditional spring-like compression to tighten the attachment of theleaflet to the stent, providing a more durable attachment than the oneachieved by suturing the leaflets to a rigid surface. Also, thereinforcement element serves as a bumper during opening to limit fullopening and reduce the accompanied shock affecting the prosthetic heartvalve at opening.

In another embodiment, the reinforcement element, which is connected tothe outer surface of the prosthetic heart valve, extends along theretaining arches and along the commissure attachment region, having awider surface than the surface of the retaining arches or the surface ofthe commissure attachment region respectively. For this reason, thereinforcement element provides a surface, sufficient to cover theretaining arches and the commissure attachment region completely. Thus,abrasion or wear of the tissue at the retaining arches or commissureattachment region respectively is avoided reliably.

Concerning the attachment of the aforementioned reinforcement elementanother advantageous embodiment includes wrapping the reinforcementelement around the retaining arches and the commissure attachment regionand securing this connection by means of wrapping and stitching. That isto say that the reinforcement element is secured firmly to the retainingarches or commissure attachment region respectively, providing a stablesurface for attachment of the prosthetic heart valve.

With regard to the reinforcement element, which is connected to theinner surface of the transition area of the prosthetic heart valve, inanother realisation, the reinforcement element consists of a foldedstrip of porcine pericardium and is attached to the transition area andstent by means of sutures. This folded strip of porcine pericardiumallows the sutures to spread out the compressive forces that secure theleaflet tissue. A tight suture attachment is required to avoid anymovement or slipping under physiological loads. If attached tightly, theloads from the leaflet will be at least partially transferred to thestent through friction and not directly to the sutures at the needleholes. This minimizes the stress concentration by spreading out thestresses, especially at the commissure attachment region. Also, thestrip of porcine pericardium serves as a bumper to absorb the impact ofthe tissue during closing and reduces the dynamic stresses transferredto the sutures. Of course, it is conceivable to use different materialsto implement the reinforcement element, which is connected to the innersurface of the prosthetic heart valve, such as wires, brackets,synthetic materials or even homograft (human) tissue. In order to reduceor prevent leakage during closed state of the prosthetic heart valve,however, the aforementioned reinforcement element has to be constructedwith a minimal size, so as to avoid the formation of a gap in betweenthe closed leaflets.

According to another embodiment of the present invention, thereinforcement elements are wrapped in tissue to avoid wear of theprosthetic heart valve tissue during operation. This is especiallyadvantageous in the case of the implementation of rigid reinforcementelements, such as wires or brackets. The tissue, wrapped around thereinforcement elements, provides a soft contact surface for theprosthetic heart valve tissue and hence prevents it from rubbing andreduces wear.

In addition to the reinforcement elements, other stent structures mayalso be wrapped in tissue or any other suitable synthetic cover. Thatis, in order to avoid abrasion of the prosthetic heart valve against thestent structure (e.g. retaining arches), the stent may be wrapped intissue or any other suitable material. In accordance with thisparticular embodiment of the present disclosure, the heart valve tissuemay not be sutured directly to the metallic stent structure but to thetissue or synthetic material covering it. This could provide a closercontact between the prosthetic heart valve and the stent so as toreliably prevent paravalvular leakage.

Yet another modification of the present disclosure includes exposing theprosthetic heart valve material surface and structure to polymericmaterial in order to reinforce it. Materials according to thisembodiment could be cyanoacrylates or polyepoxides which imply excellentbonding of body tissue and could even be used for suture-less surgery.

In a similar realisation the bendable transition portion of theprosthetic heart valve material includes a layering of various materialswith differing mechanical properties used to improve the durability ofthe prosthetic heart valve. To this end, layer materials with very highsuture retention strength overlapping the valve material in regions ofvery high stress load may be applied. As to that, material layers withhigh suture retention in lower parts of the transition area of theprosthetic heart valve may be provided, whereas the upper parts of thetransition area shall be designed to be flexible for improving thedurability of the valve. Examples for such layer materials will beexplained in more detail, with reference to the “reinforcement elements”below.

With regard to another embodiment of the present disclosure, anattachment for the prosthetic heart valve material that reduces theconcentration of stresses at the bendable transition portion isdisclosed. In this embodiment, the bendable transition portion of theprosthetic heart valve is attached to the retaining arches of the stentby folding the valve material from the outside of the stent throughslotts provided along the retaining arches. As mentioned previously, theedges of the slotted retaining arches may be rounded and smooth to avoidabrading or wearing of the valve material. In this design, there is somematerial thickness on the outside of the stent, which could impinge onthe anchoring of the stent at the position of the diseased naturalprosthetic heart valve.

To accommodate this issue, a thinning of the retaining arches relativeto the rest of the stent structure could be conducted. This would alsoallow for a recess when the stent is compressed so that the collapsedprosthesis does not require a larger delivery catheter.

According to an alternative embodiment of the present disclosure, theprosthetic heart valve is assembled with three separate pieces ofpericardial tissue. According to this, the three separate pieces ofpericardial tissue are advantageous regarding the thickness of theprosthetic heart valve tissue. When using a one piece flat tissue inorder to form the prosthetic heart valve, the thickness of the leafletscan vary and result in less desirable valve performance, unsymmetricalvalve opening and closure or less desirable hemodynamics, such as ashort durability or insufficient leaflet closure. Therefore, threesmaller pieces of pericardial tissue provide the possibility to formprosthetic heart valve with more uniform thicknesses and mechanicalproperties.

To this end, another embodiment of the present disclosure includes thateach of the three separate pieces has a flat tissue pattern in anessentially T-shirt like shape, exhibiting sleeves for connectionbetween the adjacent pieces. As mentioned previously, the adjacentpieces can be constructed, as to reinforce the contiguous edges of theadjacent pieces. To accomplish this, the sleeves of adjacent pieces canbe folded to the outside and sutured together to reinforce the joiningconnection. Attaching this reinforced area to the stent commissureattachment region helps to more uniformly distribute leaflet stressessupported by the commissure attachment.

In order to further improve the reinforcement of the contiguous edges ofthe separate pieces, in another embodiment of the present invention, thereinforcement elements consist of outer wrapping elements, wrappedaround the sleeves of the three separate pieces, in order to reinforcethe prosthetic heart valve and attach it to the commissure attachmentregion of the stent. That is, an outer wrapping element can be used inorder to further improve the durability of the prosthetic heart valve.In this regard, the outer wrapping element can consist of a piece ofpericardial tissue or a synthetic material respectively. Also, the outerwrapping element is used to attach the reinforced prosthetic heart valveto the commissure attachment region of the stent by means of sutures.Therefore, the stresses due to the suturing between the stent and theprosthetic heart valve is mainly introduced into the material of thereinforcement element, avoiding high stress concentrations in theprosthetic heart valve.

The following will make reference to the attached drawings in describingpreferred embodiments of the prosthetic heart valve, a correspondingstent and a transcatheter delivered endoprosthesis according to thepresent disclosure in greater detail.

Shown are:

FIG. 1 a roll-out view of a prosthetic heart valve according to anexemplary embodiment of the disclosure;

FIG. 2a a plan view of the upper end of the prosthetic heart valve inits closed state;

FIG. 2b a plan view of the upper end of the prosthetic heart valve inits opened state;

FIG. 3 a flat pattern of a prosthetic heart valve material piece havingan essentially t-shirt like shape for a prosthetic heart valve accordingto a further exemplary embodiment of the disclosure;

FIG. 4 a top view of the three prosthetic heart valve material piecessewn together and attached to commissure attachment regions of a stentaccording to the further exemplary embodiment of the disclosure; and

FIG. 5a a flat roll-out view of an exemplary embodiment of a firstcardiac valve stent which may be used in the endoprosthesis according toFIG. 6a, 6b, 7a or 7 b for fixing a prosthetic heart valve according toan exemplary embodiment of the disclosure;

FIG. 5b a first perspective side view of a first cardiac valve stentcapable of supporting and anchoring a prosthetic heart valve accordingto an exemplary embodiment of the disclosure, whereby the cardiac valvestent is shown in its expanded state;

FIG. 5c a second perspective side view of a first cardiac valve stentcapable of supporting and anchoring a prosthetic heart valve accordingto an exemplary embodiment of the disclosure, whereby the cardiac valvestent is shown in its expanded state;

FIG. 5d a third perspective side view of a first cardiac valve stentcapable of supporting and anchoring a prosthetic heart valve accordingto an exemplary embodiment of the disclosure, whereby the cardiac valvestent is shown in its expanded state;

FIG. 5e a plan view of the lower end of a first cardiac valve stentcapable of supporting and anchoring a prosthetic heart valve accordingto an exemplary embodiment of the disclosure, whereby the cardiac valvestent is shown in its expanded state;

FIG. 6a a first perspective side view of an endoprosthesis for treatinga narrowed cardiac valve or a cardiac valve insufficiency, where theendoprosthesis is shown in an expanded state and where theendoprosthesis comprises a cardiac valve stent and a prosthetic heartvalve according to an exemplary embodiment of the disclosure, saidcardiac valve stent is used for holding the prosthetic heart valve;

FIG. 6b a second perspective side view of an endoprosthesis for treatinga narrowed cardiac valve or a cardiac valve insufficiency, where theendoprosthesis is shown in an expanded state and where theendoprosthesis comprises a cardiac valve stent and a prosthetic heartvalve according to an exemplary embodiment of the disclosure, saidcardiac valve stent is used for holding the prosthetic heart valve;

FIG. 7a a first perspective side view of an endoprosthesis for treatinga narrowed cardiac valve or a cardiac valve insufficiency, where theendoprosthesis is shown in an expanded state and where theendoprosthesis comprises a cardiac valve stent and a prosthetic heartvalve according to an exemplary embodiment of the disclosure, saidcardiac valve stent is used for holding the prosthetic heart valve;

FIG. 7b a second perspective side view of the endoprosthesis depicted inFIG. 7a , where the endoprosthesis is shown in an expanded state andwhere the endoprosthesis comprises a cardiac valve stent and aprosthetic heart valve according to an exemplary embodiment of thedisclosure, said cardiac valve stent is used for holding the prostheticheart valve;

FIG. 8a a flat roll-out view of an exemplary embodiment of a secondcardiac valve stent, in its compressed state, which may be used in theendoprosthesis according to FIG. 11a or FIG. 11b for fixing a prostheticheart valve according to an exemplary embodiment of the disclosure;

FIG. 8b a first perspective side view of the second cardiac valve stentcapable of supporting and anchoring a prosthetic heart valve accordingto an exemplary embodiment of the disclosure, whereby the cardiac valvestent is shown in its expanded state;

FIG. 8c a second perspective side view of the second cardiac valve stentcapable of supporting and anchoring a prosthetic heart valve accordingto an exemplary embodiment of the disclosure, whereby the cardiac valvestent is shown in its expanded state;

FIG. 8d a second flat roll-out view of an exemplary embodiment of asecond cardiac valve stent, in its expanded state, which may be used inthe endoprosthesis according to FIG. 11a or FIG. 11b for fixing aprosthetic heart valve according to an exemplary embodiment of thedisclosure;

FIG. 9 a flat roll-out view of an exemplary embodiment of a thirdcardiac valve stent, in its expanded state, which may be used in anendoprosthesis for fixing a prosthetic heart valve according to anexemplary embodiment of the disclosure;

FIG. 10 a flat roll-out view of an exemplary embodiment of a fourthcardiac valve stent, in its expanded state, which may be used anendoprosthesis for fixing a prosthetic heart valve according to anexemplary embodiment of the disclosure;

FIG. 11a a first perspective side view of an endoprosthesis for treatinga narrowed cardiac valve or a cardiac valve insufficiency, where theendoprosthesis is shown in an expanded state and where theendoprosthesis comprises a cardiac valve stent and a prosthetic heartvalve according to an exemplary embodiment of the disclosure, saidcardiac valve stent is used for holding the prosthetic heart valve;

FIG. 11b a second perspective side view of the endoprosthesis depictedin FIG. 11a , where the endoprosthesis is shown in an expanded state andwhere the endoprosthesis comprises a cardiac valve stent and aprosthetic heart valve according to an exemplary embodiment of thedisclosure, said cardiac valve stent is used for holding the prostheticheart valve;

FIG. 11c a perspective top view of the endoprosthesis depicted in FIG.11a , where the endoprosthesis is shown in an expanded state and wherethe endoprosthesis comprises a cardiac valve stent and a prostheticheart valve according to an exemplary embodiment of the disclosure, saidcardiac valve stent is used for holding the prosthetic heart valve;

FIG. 12 a cross sectional view along the line A-A shown in FIG. 6b or 11b showing a first exemplary embodiment of reinforcement elements whichmay be utilized in the endoprosthesis according to the presentdisclosure for fixing a prosthetic heart valve to a cardiac valve stent;

FIG. 13 a cross sectional view along the line A-A shown in FIG. 6b or 11b showing a second exemplary embodiment of reinforcement elements whichmay be utilized in the endoprosthesis according to the presentdisclosure for fixing a prosthetic heart valve to a cardiac valve stent;

FIG. 14 a cross sectional view along the line A-A shown in FIG. 6b or 11b showing a third exemplary embodiment of reinforcement elements whichmay be utilized in the endoprosthesis according to the presentdisclosure for fixing a prosthetic heart valve to a cardiac valve stent;

FIG. 15 a cross sectional view along the line B-B shown in FIG. 6b or 11b for explaining a fourth exemplary embodiment of reinforcement elementswhich may be utilized in the endoprosthesis according to the presentdisclosure for fixing a prosthetic heart valve to a cardiac valve stent;

FIG. 16 a cross sectional view along the line B-B shown in FIG. 6b or 11b showing a fifth exemplary embodiment of reinforcement elements whichmay be utilized in the endoprosthesis according to the presentdisclosure for fixing a prosthetic heart valve to a cardiac valve stent;

FIG. 17 a cross sectional view along the line B-B shown in FIG. 6b or 11b showing a sixth exemplary embodiment of reinforcement elements whichmay be utilized in the endoprosthesis according to the presentdisclosure for fixing a prosthetic heart valve to a cardiac valve stent;

FIG. 18 a cross sectional view along the line B-B shown in FIG. 6b or 11b showing an alternative attachment solution for fixing a prostheticheart valve to a cardiac valve stent;

FIG. 19a-c the steps for connecting two separate prosthetic heart valvematerial pieces along their contiguous edges according to the secondexemplary embodiment of the prosthetic heart valve;

FIG. 20 a top view of the attachment of the prosthetic heart valve tothe commissure attachment regions of a stent according to the secondexemplary embodiment of the prosthetic heart valve;

FIG. 21 a detailed perspective view of an alternative attachment of theprosthetic heart valve to the commissure attachment regions of a stentaccording to the second exemplary embodiment of the prosthetic heartvalve.

FIG. 1 shows a view of a flat tissue pattern for a prosthetic heartvalve 100 according to an exemplary disclosed embodiment. The prostheticheart valve 100 may comprise at least two leaflets, and as shown in theexemplary embodiment of the flat tissue pattern for a prosthetic heartvalve 100 depicted in FIG. 1 three leaflets 102. Each of the leaflets102 comprises a natural tissue and/or synthetic material. The leaflets102 are attached to a skirt portion 103. As will be discussed later onin detail, the skirt portion 103 is used for mounting the prostheticheart valve 100 to a stent 10.

The leaflets 102 of the prosthetic heart valve 100 are adapted to bemoveable from a first opened position for opening the heart chamber anda second closed position for closing the heart chamber. In particular,in the implanted state of the prosthetic heart valve 100, the leaflets102 may switch between their first and second position in response tothe blood flow through the patient's heart. During ventricular systole,pressure rises in the left ventricle of the patient's heart. When thepressure in the left ventricle of the patient's heart rises above thepressure in the aorta the leaflets 102 of prosthetic heart valve 100opens, allowing blood to exit the left ventricle into the aorta. Whenventricular systole ends, pressure in the left ventricle rapidly drops.When the pressure in the left ventricle decreases, the aortic pressureforces the leaflets 102 of the prosthetic heart valve 100 to close.

FIGS. 2a and 2b respectively show a plan view of the upper end of aprosthetic heart valve 100 in the closed and opened state. In the closedposition of the prosthetic heart valve 100 (see FIG. 2a ), the threeleaflets 102 come together in the centre of the prosthetic heart valve100 thereby creating a region of sealing.

During the opening phase the leaflets pivot about a bendable transitionarea 104, as depicted in FIG. 1. The bendable transition area 104 formsa junction between the leaflets 102 and the skirt portion 103 andprogresses in a substantial U-shaped manner, similar to the cusp shapeof a natural aortic or pulmonary heart valve. Still within the openingphase, the commissure region 105 and the leaflets 102 move radiallyoutwards opening the valve in response to increased differentialpressure allowing blood to flow through the prosthesis.

In the exemplary embodiment depicted in FIG. 1, the prosthetic heartvalve 100 is made of one piece of flat pericardial tissue. Thispericardial tissue can either be extracted from an animal's heart(xenograft) or a human's heart (homograft). The extracted tissue may becut by a laser or knife or might be pressed in order to form a flattissue pattern representing each of the leaflets 102 and the skirtportion 103. After said forming of the flat tissue pattern, the so madeheart valve tissue may be sewn into a cylindrical or conical shape,ready to be attached to a corresponding stent structure 10. As will bediscussed in detail with respect to FIGS. 6a, 6b , the skirt portion 103represents an area of the prosthetic heart valve 100 that is used forconnecting the prosthetic heart valve 100 to a stent 10, for example, bymeans of sutures 101.

As can be seen from FIGS. 1 and 2, the pattern of the prosthetic heartvalve 100 represents each of the leaflets 102, commissure region 105 andthe skirt portion 103 of the intended prosthetic heart valve 100. Hence,the flat tissue pattern is designed so as to form the leaflets 102 in amanner, having three half-moon shaped leaflets like the aortic orpulmonary heart valve. The leaflets 102 can be designed in variousshapes such as the geometry of an ellipse, U-shape or substantiallyoval. Preferably the three leaflets 102 are formed in such a manner thatall of them have the same general shape.

Another aspect shown by FIG. 1 is a flared lower end section ofprosthetic heart valve 100. As will be explained in more detail below,such a flared lower end section may be advantageous in order to fit theprosthetic heart valve 100 to an annular collar 40 of a respectivecardiac heart valve 10. Alternatively, it is further conceivable toproduce a prosthetic heart valve 100 comprising a tapered lower endsection. A flare or taper at the lower end section of the prostheticheart valve 100 may be adapted to the geometry of the blood vessel atthe implantation site of the prosthesis, so as to obtain the mostreliable fit of said prosthesis to said blood vessel.

Between the leaflets 102 and the skirt portion 103, the valve patternshows the bendable transition area 104 progressing in a substantialU-shaped manner, similar to the cusp-shape of a natural aortic orpulmonary heart valve.

As can be derived from FIG. 2a , the leaflet portion of the prostheticheart valve 100 is designed to provide redundant coaptation forpotential annular distortion. Accordingly, the redundant coaptation mayreduce stress on the leaflets 102 and assures a reliable closure of theheart chamber in the second closed position of the leaflets 102. Thisredundant coaptation provides for more surface contact between theleaflets, allowing for the prosthetic heart valve of the presentdisclosure to be implanted in a distorted valve annulus, stillmaintaining sufficient coaptation.

Although not depicted in FIG. 1, the prosthetic heart valve 100 cancomprise a plurality of fastening holes 106 provided along theprogression of the transition area 104. These fastening holes 106 areintroduced into the tissue material of the prosthetic heart valve 100 bymeans of laser cutting for strengthening the tissue area around thefastening holes 106. Alternatively, however, it is conceivable thatfastening holes 106 are introduced by the needle during the sewingprocess.

The bendable transition area 104 shown in FIG. 1 may include a layeringof various materials with differing mechanical properties. Accordingly,the lower parts, particularly associated with retaining arches of acardiac valve stent, may be more rigid to provide high suture retention,whereas the upper parts, particularly associated with a commissureattachment region 11 b of the stent, may be designed to be more flexiblein order to support the movement of the leaflets 102. On the same note,the leaflets 102 and the leaflet support portion 103 may exhibitdifferent stability characteristics. This might be achieved by the useof different cross-linking processes for the leaflets 102 or the leafletsupport portion 103 respectively. Alternatively, the leaflets 102 or theleaflet support portion 103 could be reinforced by attaching smallsheets of tissue or synthetic material in order to increase themechanical stability.

As the size and diameter of different blood vessels of differentpatients varies to a certain extent, it may be advantageous to provideprosthetic heart valves 100 of different designs. In particular, tissuematerial with a thickness of 160 μm to 300 μm, more preferably 220 μm to260 μm may be used, depending on the particular tissue material used tomanufacture the prosthetic heart valve. Furthermore, the prostheticheart valve 100, according to the present disclosure, may have adiameter ranging form 19 mm to 28 mm.

Reference is made in the following to FIGS. 6a, b which respectivelyshow a first and second perspective side view of an endoprosthesis 1 fortreating a narrowed cardiac valve or a cardiac valve insufficiency,where the endoprosthesis 1 comprises an exemplary embodiment of acardiac valve stent 10 for holding a prosthetic heart valve 100. In theillustrations according to FIGS. 6 a, b, the endoprosthesis 1 is shownin an expanded state.

As can be seen from the illustrations according to FIGS. 6 a, b, in theaffixed state of the prosthetic heart valve 100, the transition area 104of the prosthetic heart valve 100 extends along the retaining arches 16a, 16 b, 16 c and, in particular, along the lower leaflet attachmentregion 11 c and the commissure attachment region 11 b of the retainingarches 16 a, 16 b, 16 c of the stent 10. The bendable transition area104 of the prosthetic heart valve 100 is attached to retaining arches 16a, 16 b, 16 c of the stent 10 such as to enable the leaflets 102 of theprosthetic heart valve 100 to bend inwards in a controlled manner to thecentre of the stent 10 forming the valvular leaflets 102.

For adapting the prosthetic heart valve 100 to a corresponding stent 10so that the valvular leaflets 102 are properly formed and prostheticheart valve is properly fitted to the stent structure, the pattern ofthe flat-tissue material of the prosthetic heart valve 100 shall be cutso as to incorporate the leaflet structures, the annular skirt portion103 and the transition area 104 in between them. In other words, afterthe prosthetic heart valve material is sewn into its cylindrical orconical shape, the valve exhibits a flared portion at the lower end.This flared geometry fits the structure of the stent 10 and isconstructed to optimally fit the vascular wall at the implantation siteof the diseased heart valve.

In the exemplary embodiment of the transcatheter deliveredendoprosthesis 1 depicted in FIGS. 6 a, b, the prosthetic heart valve100, which is affixed to the stent 10, consists of a one piece flatpericardial tissue material extracted from an animal or humanpericardial sack and cut into a pattern representing each of the threeleaflets 102 and the skirt portion 103, wherein the pattern is sewn intoa cylindrical shape before attachment to the stent 10. In addition, theprosthetic heart valve 100 includes a transition area 104 which isconnected to the retaining arches 16 a, 16 b, 16 c and commissureattachment regions 11 b of the stent. The transition area 104 connectsthe leaflets 102 with the skirt portion 103. In particular, thetransition area 104 is essentially U-shaped, similar to the cusp shapeof a natural aortic or pulmonary heart valve. For this reason, thetransition area 104 allows for an opening and closing motion of theleaflets 102, causing minimal stresses within the biological prostheticheart valve tissue.

Upon assembly of this tissue pattern (see FIG. 1) to a stent 10, theregions of tissue between the retaining arches become the valve leaflets102. These leaflets can be folded inwards so as to form threeessentially closed leaflets. In case of a pressure gradient in adownstream direction (in response to a rising blood pressure in theheart chamber), the leaflets 102 are forced apart, in the direction ofthe stent 10, enabling blood to exit the heart chambers. On the otherhand, if there is a pressure gradient in the opposite, upstreamdirection (retrograde gradient, in response to an intake pressure in theheart chamber), the blood rushes into the leaflets 102, thereby pressingthe leaflets 102 together in the centre of stent 10 and closing thetranscatheter delivered endoprosthesis 1.

As has been described in more detail with reference to FIGS. 5a-e andFIGS. 8 to 10, a suitable stent 10, to which the prosthetic heart valve100 may be attached for forming an endoprosthesis 1, may include anannular collar 40 arranged to a lower section of stent 10. The annularcollar 40 of the stent 10 serves as an additional anchoring measure tohold the transcatheter delivered endoprosthesis 1 in a desired locationat the site of the diseased heart valve. In the exemplary embodiment ofthe transcatheter delivered endoprosthesis 1 depicted in FIGS. 6 a, b,FIGS. 7a, b and FIGS. 11a to 11c , the annular collar 40 of the stent100 has a flared shape.

Accordingly, the lower part of leaflet support portion 103 of theprosthetic heart valve 100 affixed to the stent 10 also exhibits anextended diameter in order to accommodate the flared shape of theannular collar 40.

The prosthetic heart valve 100 is fixed to the stent 10 by means ofsutures, threads or wires 101 which are attached to the skirt portion103 and/or the transition area 104 of the prosthetic heart valve 100.The skirt portion 103 serves for keeping the prosthetic heart valve 100in a predefined position relative to the stent 10.

As will be described in more detail below, a suitable stent 10, to whichthe prosthetic heart valve 100 may be attached for forming anendoprosthesis 1, may include an annular collar 40 arranged to a lowersection of stent 10. The annular collar 40 of the stent 10 serves as anadditional anchoring measure to hold the transcatheter deliveredendoprosthesis 1 in a desired location at the site of the diseased heartvalve.

As can be seen from the illustrations in FIGS. 6 a, b, the skirt portion103 of the prosthetic heart valve 100 may also be attached to theannular collar 40 of the stent 10 by means of sutures, threads or wires101. For this purpose, multi-filament sutures 101 of a diameter up to0.2 mm, preferably between 0.1 mm and 0.2 mm may be used.

Moreover, a common running stitch pattern may be used to obtain saidbonding. According to the disclosure, the stitch pattern is preferably alocking stitch or a blanket stitch respectively. Of course, any othersuitable stitch pattern (i.e.

overlocking stitch, slipstitch or topstitch) is also possible.

As indicated by FIGS. 6a and 6b , the bendable transition area 104 ofthe prosthetic heart valve may be attached to retaining arches 16 a, 16b, 16 c of the stent 10 by means of sutures 101, having a diameterlarger than the diameter of the sutures 101 used for attachment of theprosthetic heart valve to an annular collar 40 of the stent 10. Due tothis, the prosthetic heart valve 100 can be reliably attached to thestent without adding too much bulk to the stent 10, in order to collapsethe endoprosthesis to a small diameter.

In the exemplary embodiment of the transcatheter deliveredendoprosthesis 1 depicted in FIGS. 6 a, b, the annular collar 40 of thestent 100 has a flared shape. Accordingly, the lower part of skirtportion 103 of the prosthetic heart valve 100 affixed to the stent 10also exhibits an extended diameter in order to accommodate the flaredshape of the annular collar 40.

The scope of the present disclosure will become more clear byconsidering some of the possible embodiments of a stent 10 with theprosthetic heart valve 100 attached thereto thereby forming anendoprosthesis. Hence, reference is made in the following to FIGS. 5a-efor describing an exemplary embodiment of a stent 10 to which aprosthetic heart valve 100 may be affixed in order to form thetranscatheter delivered endoprosthesis 1 depicted in FIGS. 6 a, b.

In particular, FIG. 5b is a first perspective side view of a cardiacvalve stent 10, whereby the cardiac valve stent 10 is shown in itsexpanded state. Second and third side views of the cardiac valve stent10 in its expanded state are shown in FIGS. 5c and 5 d.

On the other hand, FIG. 5e shows a plan view of the lower end of thecardiac valve stent 10 according to the exemplary embodiment of thedisclosure in its expanded state, whereas a flat roll-out view of astent 10 according to the exemplary embodiment is shown in FIG. 5 a.

The stent 10 depicted in FIGS. 5a-e is also provided with an annularcollar 40 which is arranged at the lower end section of the stent body.The at least one collar 40 may serve as an additional anchoring measurefor the stent 10.

In addition, the stent 10 according to the exemplary embodiment has atotal of three positioning arches 15 a, 15 b, 15 c, which undertake thefunction of automatic positioning of the stent 10. Each of thepositioning arches 15 a, 15 b, 15 c has a radiused head portion 20,which engages in the pockets of the native heart valve being treatedduring positioning of the stent 10 at the implantation site in theheart.

The exemplary embodiment of the stent 10 also includes radial arches 32a, 32 b, 32 c. In particular, the stent 10 has three radial arches 32 a,32 b, 32 c, with each arch 32 a, 32 b, 32 c located between the two arms15 a, 15 a′, 15 b, 15 b′, 15 c, 15 c′ of each positioning arch 15 a, 15b, 15 c. Each radial arch 32 a, 32 b, 32 c has a shape that is roughlyinverse to each positioning arch 15 a, 15 b, 15 c and extends in theopposite direction to each one of the positioning arches 15 a, 15 b, 15c.

In addition, the stent 10 according to the exemplary embodiment depictedin FIGS. 5a-e is provided with corresponding retaining arches 16 a, 16b, 16 c. Each one of the retaining arches 16 a, 16 b, 16 c is allocatedto one of the positioning arches 15 a, 15 b, 15 c. Also, according tothis exemplary embodiment of the stent 10, a number of commissureattachment regions 11 b with a number of additional fastening holes 12 cis configured at one end of each arm 16 a′, 16 a″, 16 b′, 16 b″, 16 c′,16 c″ of the retaining arches 16 a, 16 b, 16 c.

In addition to the commissure attachment regions 11 b, the stent 10 alsocomprises second lower leaflet attachment regions 11 c for additionalfastening of the tissue component(s) of a prosthetic heart valve 100(see FIGS. 6a, b ). In this regard, the stent 10 according to theexemplary embodiment depicted in FIGS. 5a-e has a configuration with anumber of attachment regions 11 b, 11 c to attach the material of aprosthetic heart valve 100.

The stent 10 may also be provided with leaflet guard arches, wherein oneleaflet guard arch may be provided in between each positioning arch 15a, 15 b, 15 c. The structure and function of the leaflet guard archeswill be described later with reference to FIGS. 7a and 7b . Hence,although for reasons of clarity not explicitly shown, in the stentdesign according to the exemplary embodiment depicted in FIGS. 5a -e,one leaflet guard arch may be allocated to each positioning arch 15 a,15 b, 15 c.

The exemplary embodiment of the sent 10 is characterized by a specificstructure of the respective arms 16 a′, 16 a″, 16 b′, 16 b″, 16 c′, 16c″ of the retaining arches 16 a, 16 b, 16 c. In detail, in the expandedstate of the stent 10, the respective arms 16 a′, 16 a″, 16 b′, 16 b″,16 c′, 16 c″ of the retaining arches 16 a, 16 b, 16 c have a shapesimilar to a prosthetic heart valve 100. Furthermore, the respectivearms 16 a′, 16 a″, 16 b′, 16 b″, 16 c′, 16 c″ of the retaining arches 16a, 16 b, 16 c are provided with a number of lower leaflet attachmentregions 11 c, each having a number of additional fastening holes 12 a oreyelets provided for fastening the tissue component(s) of a prostheticheart valve 100. These additional fastening holes 12 a or eyeletsprovide attachment points for the bendable transition area 104 of aprosthetic heart valve 100 attached to the stent 10.

As will be described in more detailed below, in an alternativeembodiment, the respective arms 16 a′, 16 a″, 16 b′, 16 b″, 16 c′, 16 c″of the retaining arches 16 a, 16 b, 16 c may be provided with a numberof fastening notches which can be used to fix the bendable transitionarea 104 to stent 10. Thus, in this alternative embodiment, there are noadditional fastening holes 12 a needed along the respective arms 16 a′,16 a″, 16 b′, 16 b″, 16 c′, 16 c″ of the retaining arches 16 a, 16 b, 16c.

According to the stent designs of the embodiments depicted in FIGS. 5a-eand FIGS.

8 to 10, in the expanded state of the stent 10, the respective arms 16a′, 16 a″, 16 b′, 16 b″, 16 c′, 16 c″ of the retaining arches 16 a, 16b, 16 c have a shape that substantially matches the transition area 104of a prosthetic heart valve 100 attached to the stent 10 (see FIG. 6a, bor 11 a, b).

This specific design of the respective arms 16 a′, 16 a″, 16 b′, 16 b″,16 c′, 16 c″ of the retaining arches 16 a, 16 b, 16 c has valvedurability advantages. The so formed arms 16 a′, 16 a″, 16 b′, 16 b″, 16c′, 16 c″ of the retaining arches 16 a, 16 b, 16 c serve for supportingthe skirt portion 103 and edge of the leaflets 102 of a prosthetic heartvalve 100 attached to the stent 10.

As depicted, for example, in FIGS. 6a, b and 11 a, b, the respectivearms 16 a′, 16 a″, 16 b′, 16 b″, 16 c′, 16 c″ of the retaining arches 16a, 16 b, 16 c follow the shape of the bendable transition area 104 of aprosthetic heart valve 100 affixed to the stent 10 in its expandedstate. Furthermore, the respective arms 16 a′, 16 a″, 16 b′, 16 b″, 16c′, 16 c″ of the retaining arches 16 a, 16 b, 16 c are designed to havea minimized unsupported gap from one arm to the other arm of a retainingarch 16 a, 16 b, 16 c at the location behind the positioning arches 15a-c.

In detail and as depicted in the cutting pattern shown in FIG. 5a , therespective arms 16 a′, 16 a″, 16 b′, 16 b″, 16 c′, 16 c″ of theretaining arches 16 a, 16 b, 16 c are provided with a plurality ofbending edges 33. These bending edges 33 divide each arm 16 a′, 16 a″,16 b′, 16 b″, 16 c′, 16 c″ into a plurality of arm segments. The armsegments of a single arm 16 a′, 16 a″, 16 b′, 16 b″, 16 c′, 16 c″ of theretaining arches 16 a, 16 b, 16 c are interconnected therebyconstituting a retaining arch arm which describes an essentiallystraight line in the not-expanded state of the stent 10. In this regard,reference is also made to the cutting pattern depicted in FIG. 5a whichshows the uncurved configuration of the respective arms 16 a′, 16 a″, 16b′, 16 b″, 16 c′, 16 c″ of the retaining arches 16 a, 16 b, 16 c.

When manufacturing the stent 10, the stent structure and in particularthe structure of the retaining arches 16 a, 16 b, 16 c is programmedsuch that the respective arms 16 a′, 16 a″, 16 b′, 16 b″, 16 c′, 16 c″of the retaining arches 16 a, 16 b, 16 c have a curved shape in theexpanded state of the stent 10. The shape of the respective arms 16 a′,16 a″, 16 b′, 16 b″, 16 c′, 16 c″ of the retaining arches 16 a, 16 b, 16c is such defined that the arms follow the shape of the transition area104 of a prosthetic heart valve 100 to be affixed to the stent 10 (seeFIGS. 6a and 6b ).

Hence, the respective arms 16 a′, 16 a″, 16 b′, 16 b″, 16 c′, 16 c″ ofthe retaining arches 16 a, 16 b, 16 c of the stent 10, onto which thetransition area 104 of a prosthetic heart valve 100 is sewn or sewable,will change their shape when the stent 10 expands, wherein the retainingarches 16 a, 16 b, 16 c are curved in the expanded state of the stent10, but relatively straight when the stent 10 is collapsed.

As can be seen, for example, in FIGS. 5b -d, the curvature of therespective arms 16 a′, 16 a″, 16 b′, 16 b″, 16 c′, 16 c″ of theretaining arches 16 a, 16 b, 16 c is achieved by segmenting the arms 16a′, 16 a″, 16 b′, 16 b″, 16 c′, 16 c″. In detail, the arms 16 a′, 16 a″,16 b′, 16 b″, 16 c′, 16 c″ are segmented by providing a plurality ofbending edges 33. In the expanded state of the stent 10, two neighboringarm segments are angled relative to each other, wherein the bendingpoint of these two neighboring arm segments is defined by the bendingedge 33 which is provided in between the both neighboring arm segments.Hence, the greater the number of bending edges 33 provided in an arm 16a′, 16 a″, 16 b′, 16 b″, 16 c′, 16 c″ of a retaining arch 16 a, 16 b, 16c, the greater the number of arm segments which may extend in differentdirections in the expanded state of the stent 10. In this respect, theshape of the respective arms 16 a′, 16 a″, 16 b′, 16 b″, 16 c′, 16 c″ ofthe retaining arches 16 a, 16 b, 16 c can be precisely adapted to theshape of transition area 104 of a prosthetic heart valve 100 to beaffixed to the stent 10. Also, it should be noted that the embodimentsdepicted in FIGS. 8 to 10 show an even higher number of bending edges 33providing a plurality of arm segments. Further to this, the bendingedges 33 depicted in FIGS. 8 to 10 are formed so as to provide aplurality of fastening notches along the retaining arches 16 a, 16 b, 16c, as will be described in more detail below.

The stent 10 depicted in FIGS. 5a-e is also provided with an annularcollar 40 which is arranged at the lower end section of the stent body.The at least one annular collar 40 may serve as an additional anchoringmeasure for the stent.

In the embodiment depicted in FIGS. 6a and 6b , the stent 10 correspondsto a stent pursuant the exemplary embodiment previously described withreference to FIGS. 5 a-e. On the other hand, the prosthetic heart valve100 affixed to the stent 10 corresponds to the exemplary embodiment ofthe prosthetic heart valve 100 previously described with reference toFIG. 1 and FIGS. 2 a, b.

Hence, as shown in the exemplary embodiment of the transcatheterdelivered endoprosthesis 1 depicted in FIGS. 6 a, b, the prostheticheart valve 100 affixed to the stent 10 comprises three leaflets 102made from a biological or synthetic material.

To reduce longitudinal displacement of the prosthetic heart valve 100relative to the stent 10, the stent 10 comprises a plurality offastening portions in the form of lower leaflet attachment regions 11 c,essentially extending in the longitudinal direction L of stent 10. Inaddition, the stent 100 is provided with commissure attachment regions11 b. By means of the lower leaflet attachment regions 11 c and thecommissure attachment regions 11 b (both acting as fastening portion),the tissue components of the prosthetic heart valve 100 are affixed tothe stent 10.

In detail, the prosthetic heart valve 100 is fastened to the stent 10 bymeans of sutures 101, threads or a thin wire which is guided throughfastening holes 12 a, 12 c of the lower leaflet attachment regions 11 cand the commissure attachment regions 11 b respectively. This allowsfixing of the tissue components of the prosthetic heart valve 100 to thestent 10 at a predefined position relative to the stent 10.

Alternatively, as will be described with reference to FIGS. 8 to 10, thesutures 101, threads or wires may be guided by fastening notchesprovided along the retaining arches 16 a, 16 b, 16 c, instead of theaforementioned fastening holes 12 a. Hence, in the alternativeembodiments according to FIGS. 8 to 10, the fastening holes 12 a of thelower leaflet attachment region 11 c are replaced by notches (providedby bending edges 33), whereas the commissure attachment region 11 b maystill be provided with fastening holes 12 c.

It can further be seen from the FIG. 6a or FIG. 6b illustration how theprosthetic heart valve 100 can be affixed to the stent 10 by means ofsutures 101. In the depicted embodiment, a pericardial prosthetic heartvalve 100 is used which is sewn to fastening holes 12 a, 12 c providedin the fastening portions of the retaining arches 16 a, 16 b, 16 c, i.e.the lower leaflet attachment regions 11 c on the one hand and in thecommissure attachment regions 11 b on the other hand. In order toimprove the attachment of the prosthetic heart valve 100 to the stent10, the skirt portion 103 may be sewn to the annular collar 40 as wellas other parts of the stent structure. The prosthetic heart valve 100may be tubular with a substantially circular cross-section.

On the other hand, it is conceivable to mount the prosthetic heart valve100 to the outer surface of a support stent 1. That is, the skirtportion 102 could be in direct contact with the diseased native heartvalve and could be attached to the stent 10 by means of sutures.Mounting the prosthetic heart valve 100 to the outer surface of thestent 10 supports the load transfer from the leaflet 102 to the stent 1.This greatly reduces stresses on the leaflets 102 during closing andconsequently improves the durability thereof. Also, it is possible todesign the valve to obtain improved hemodynamics in the case of mountingthe skirt portion and commissures to the outer surface of the stent.Additionally, the heart valve material which is in direct contact withthe diseased native heart valve provides a good interface for sealingagainst leakage (i.e., paravalvular leakage), tissue in-growth andattachment.

The material for the prosthetic heart valve 100 and, in particular thematerial for the leaflets 102 of the prosthetic heart valve 100 can bemade from synthetics, animal valves or other animal tissues such aspericardium. The animal tissues can be from a number of types ofanimals. Preferably, the leaflet material of the prosthetic heart valve100 is from either bovine or porcine pericardium, but other animals canalso be considered, for example equine, kangaroo, etc.

Reference is made in the following to FIGS. 12 to 17 for describingexemplary embodiments of reinforcement elements 107.1 to 107.8 which maybe utilized in the endoprosthesis 1 according to the present disclosure.The reinforcement elements 107.1 to 107.8 may reduce the stressconcentration in the tissue material of the prosthetic heart valve 100at the connection between the bendable transition area 104 and the lowerleaflet attachment region 11 c (FIGS. 12 to 14) and/or the commissureattachment regions 11 b (FIGS. 15 to 17) of the stent 10.

The reinforcement elements 107.1 to 107.8 can be at discrete locationsor continuously along the path of the stitching. For example, they canbe placed opposite to the retaining arches of the stent on the otherside of the prosthetic heart valve material. The depicted reinforcementelements 107.1 to 107.8 are applied in order to strengthen theattachment to the stent and reduce stress concentrations in the leafletmaterial that would occur by suturing directly to the bendabletransition portion 104 or leaflet support portion 103 respectively.Further to this, the reinforcement elements 107.1 to 107.8 may avoiddirect contact between knots of the sutures and the tissue of theprosthetic heart valve. Also, direct contact between the heart valvetissue and the stent structure or any other metallic component of theendoprosthesis can be avoided by the reinforcement elements.

The reinforcement elements 107.1 to 107.8 are preferably designed withrounded edges to avoid abrasion of the valve tissue during opening andclosing of the prosthetic heart valve 100.

In more detail, FIG. 12 shows a cross sectional view along the line A-Ain FIG. 6b or FIG. 11b respectively, i.e. a cross sectional view of oneretaining arch 16 a, 16 b, 16 c of the stent 10 utilized in anendoprosthesis 1 of the present disclosure. As depicted in FIG. 12, afirst exemplary embodiment of reinforcement elements 107.1 may beutilized for fixing the prosthetic heart valve 100 to the stent 10.

According to this exemplary embodiment, the connection of the prostheticheart valve tissue to the stent 10 is reinforced by means of at leastone reinforcement element in the form of a inner cushion 107.1 which isintended to reduce stress concentrations in the tissue material of theprosthetic heart valve 100, said that stress concentrations may occurfrom direct stitching in the tissue material of the prosthetic heartvalve 100. The at least one reinforcement element in the form of theinner cushion 107.1 is placed between a suture 101.1 and the tissuematerial of the prosthetic heart valve 100. In this respect, any stresscaused by the suture 101.1 is distributed over a larger area of thetissue material of the prosthetic heart valve 100. The at least onereinforcement element in the form of the inner cushion 107.1 is placedopposite to the corresponding retaining arch 16 a, 16 b, 16 c of thestent 10 on the other side of the tissue material of the prostheticheart valve 100. That is, the at least one reinforcement element in theform of the inner cushion 107.1 is mounted to the inner surface of thebendable transition area 104 of the prosthetic heart valve 100. The atleast one inner cushion 107.1 representing a first embodiment of thereinforcement elements may be folded in such a way that at least oneround edge 108 is formed. This at least one round edge 108 is designedto avoid abrasion of tissue material of the leaflets 102 during openingand closing of the prosthetic heart valve 100.

The reinforcement element in the form of the inner cushion 107.1 may bemade of one or multiple layer materials, consisting of materials likepolyester velour, PTFE, pericardial tissue, or any other materialsuitable for forming round edges, distributing or buffering stresses inthe tissue material of the prosthetic heart valve 100. The reinforcementelement in the form of the inner cushion 107.1 can be applied to spanacross the gap formed between the lower end of two neighbouring arms 16a′, 16 a″; 16 b′, 16 b″; 16 c′, 16 c″ of one retaining arches 16 a, 16b, 16 c (see FIG. 6a ) for supporting the tissue material of theprosthetic heart valve 100 across the gap.

Reference is further made to FIG. 15, which is a cross sectional viewalong the line B-B (commissure attachment region 11 b) shown in FIG. 6bor 11 b for explaining a second exemplary embodiment of thereinforcement elements which may be utilized in the transcatheterdelivered endoprosthesis 1 of the present disclosure, for fixing aprosthetic heart valve 100 to a cardiac valve stent 10.

Again, the reinforcement element may be made of one or multiple layermaterials and consisting of materials like polyester velour, PTFE,pericardial tissue or any other material suitable for forming roundedges. As shown in FIG. 15, at the upper end section of the prostheticheart valve 100, the tissue material of the prosthetic heart valve 100may be attached to the commissure attachment region 11 b in such amanner that when the leaflets 102 are folded together, during closure ofthe heart valve, a small cavity 109 is created. Inside this cavity 109,a reinforcement element in the form of an inner cushion 107.2 isinserted. It has to be noted that the cavity 109 is formed, so as to beas small as possible in order to avoid leakage during the closing phaseof the heart valve prosthesis 1.

FIG. 13 is a cross sectional view along the line A-A shown in FIG. 6b or11 b for explaining a third exemplary embodiment of reinforcementelements which may be utilized in the endoprosthesis 1 according thepresent disclosure. According to this exemplary embodiment, thereinforcement element may consist of a wire rail 107.3 which issubstantially at the same place as the reinforcement elements consistingof an inner cushion 107.1 illustrated in FIG. 12. In this case, thesutures 101.1 are coiled around the wire rail 107.3 on the inner surfaceof the prosthetic heart valve 100, whilst on the outer surface of thebiological prosthetic heart valve, the sutures 101.1 are attached to aretaining arch 16 a, 16 b, 16 c by means of a suitable stitch pattern.That is, the wire rail 107.3 is mounted to the inner surface of thebendable transition area 104 of the prosthetic heart valve. The wirerail 107.3 is preferably made of Nitinol, thus allowing for the wirerail 107.3 to collapse together with the stent 10. Again, thereinforcement element of the third embodiment is designed with roundededges to avoid abrasion of the leaflet tissue during opening and closingof the prosthetic heart valve 100.

FIG. 14 is a cross sectional view along the line A-A shown in FIG. 6b or11 b for explaining a fourth exemplary embodiment of reinforcementelements which may be utilized in the endoprosthesis 1 according to thepresent disclosure. Hence, instead of using inner cushions 107.1, 107.2which consist of materials like polyester velour or PTFE, thereinforcement element, according to the fourth exemplary embodiment, canbe arranged as essential copies of the retaining arches 16 a, 16 b, 16c. In this embodiment, however, the reinforcement element is an innerattachment rail 107.4 which is thinner than a corresponding retainingarch 16 a, 16 b, 16 c since a thick material would inhibit theendoprosthesis 1 from being collapsed to a small size. In particular,the inner attachment rail 107.4 has the same fastening holes 12 a andnotches longitudinally distributed at given locations as thecorresponding retaining arch 16 a, 16 b, 16 c.

Moreover, the inner attachment rail 107.4 is placed on the inner surfaceof the tissue material of the prosthetic heart valve 100, opposite tothe retaining arches 16 a, 16 b, 16 c. Thus the prosthetic heart valve100 is clamped in between the retaining arches 16 a, 16 b, 16 c and theinner attachment rail 107.4, wherein the retaining arches 16 a, 16 b, 16c and the inner attachment rail 107.4 are connected by means of sutures101.1.

In an alternative embodiment, however, the connection between retainingarches 16 and the inner attachment rail 107.4 may utilize rivets,welding or soldering, so as to clamp the biological prosthetic heartvalve tissue without penetrating it with needles or suture. In turn, itis preferable, that the inner attachment rail 107.4 may be made ofNitinol, in order to allow simultaneously collapsing with the stent 10.

Of course, the edges of the inner attachment rail 107.4 may be roundedin order to prevent abrasion of the leaflets 102. In addition, the innerattachment rail 107.4 could be wrapped in tissue or synthetic materialto further reduce the potential wear during the contact with the leafletmaterial upon the heart valve operation.

FIG. 16 shows a cross sectional view along the line B-B shown in FIG. 6bor 11 b for explaining a fifth exemplary embodiment of reinforcementelements which may be utilized in the endoprosthesis 1 of the presentdisclosure.

As depicted in FIG. 16, the reinforcement element according to thisexemplary embodiment is an outer wrapping element 107.5 attached to theback side of the prosthetic heart valve tissue, at the commissureattachment region 11 b of the stent 10. The leaflets 102 are foldedwithout forming a cavity. Rather, the outer wrapping element 107.5 isclamped on the outer surface of the biological prosthetic heart valve100, more particularly to the outer surface of the bendable transitionarea 104, pressing the leaflets 102 together. Thereby, a strengthenedregion is created by folding the prosthetic heart valve tissue andwrapping it with the outer wrapping element 107.5.

The outer wrapping element 107.5 is attached the commissure attachmentregion 11 b by means of sutures 101.1. Additional lateral sutures 101.2are provided to press the outer wrapping element 107.5 onto the outersurface of the bendable transition area 104 of the prosthetic heartvalve 100.

The outer wrapping element 107.5 is preferably made of a polymermaterial such as PTFE, PET fabric or sheet or a piece of pericardialtissue. However, it could also be a more rigid u-shaped clip or bendablematerial that can pinch the folded tissue material of the prostheticheart valve 100 without the use of additional lateral sutures 101.2. Inaddition, this outer wrapping element 107.5 acts as a bumper to limitthe opening of the leaflets 102 in order to prevent them from hittingstent 10.

The dashed lines in FIG. 16 represent the closed position of theleaflets 102.

FIG. 18 shows an alternative attachment solution where the prostheticheart valve 100 is mounted to the stent 10 from the outside. For thispurpose, the tissue material of the prosthetic heart valve 100 is foldedand passes through slots 110 provided in the retaining arches 16 a, 16b, 16 c. The edges of the slots 110 are preferably rounded and smooth toavoid abrading or wearing the tissue material of the prosthetic heartvalve 100. Furthermore, to further reduce wear of the tissue, the slots110 could be wrapped in thin pericardial tissue. In this design, thereis some material thickness on the outside of the stent 10, which couldimpinge on the anchoring of the stent 10 at the position of the diseasednatural prosthetic heart valve.

One embodiment might include thinning the retaining arches 16 a, 16 b,16 c on the outer surface relative to the rest of the stent structure,to accommodate the tissue material on the outside surface. This wouldalso allow for a recess when the stent 10 is compressed so that thecollapsed prosthesis does not require a larger delivery catheter.

FIG. 17 is a cross sectional view along the line B-B depicted in FIG. 6bor 11 b showing a sixth exemplary embodiment of reinforcement elements107.6, 107.7 which may be utilized in the endoprosthesis accordingpresent disclosure.

In detail, FIG. 17 shows an embodiment where reinforcement elements107.6 and 107.7 are attached to the inner surface and the outer surfaceof the transition area 104 of the prosthetic heart valve 100. AlthoughFIG. 17 only shows a cross sectional view along the line B-B, it shouldbe noted that the depicted sixth embodiment of the reinforcementelements may also be applied along the retaining arches 16 a, 16 b, 16 c(line A-A) of the stent. In this regard, the outer reinforcement element107.6 may consist of a wide strip of 200 μm thick porcine pericardiumthat is long enough to cover the entire length of the retaining arches16 a, 16 b, 16 c (lower leaflet attachment region 11 c) and thecommissure attachment region 11 b. This strip of pericardium which formsthe outer reinforcement element 107.6 can be cut into three shortsegments of about 5 mm each to match the length of the commissureattachment region 11 b and three long segments of about 45 mm each tomatch the length along the retaining arches 16 a, 16 b, 16 c (lowerleaflet attachment region 11 c) from one commissure attachment region 11b to the adjacent.

The 4 mm wide porcine pericardium outer reinforcement element 107.6 maybe folded in half and sutured using a fine clinging suture 101. 4 (e.g.a 8-0 suture) with a running stitch very close to the free edges. Thesutured outer reinforcement element 107.6 is then placed along the innersurface of the retaining arches 16 a, 16 b, 16 c and/or the commissureattachment region lib with a 8-0 running stitch placed along the stentsurface. The outer reinforcement element 107.6 is sutured to the stentto line the inner surface using 6-0 surrounding sutures 101.3 andzig-zag crossing stitches that wrap around the commissure attachmentregion 11 b and/or the retaining arches 16 a, 16 b, 16 c (not throughthe eyelets).

With regards to the inner reinforcement element 107.7, the material ispreferably a strip of 200 μm porcine pericardium, which is about 3.5 mmwide and cut and overlapped or rolled to three layers. The length of thepiece of tissue depends on whether only the commissure attachment region11 b or the retaining arches 16 a, 16 b, 16 c are reinforced. For onlythe commissure attachment region 11 b, three short segments of about 5mm are needed. The strip is held in the overlapped or rolled shape byclinging sutures 101.4 with an 8-0 running stitch. The innerreinforcement element 107.7 may be constructed such as to exhibitminimal size to avoid causing too big of a cavity 109 in between theleaflets 102 during closure of the prosthetic heart valve 100. The innerreinforcement element 107.7 is secured on the inner surface of thebendable transition area 104 of the prosthetic heart valve 100 and tothe stent 10 through the eyelets 12 a. Preferably, 4-0 sutures 101.1with a locking stitch on the outer diameter are used for this purpose.These sutures 101.1 are the most critical in the assembly and need to bevery tight with no slack and locking. Instead of a single 4-0 suture101.1, it is contemplated that two 6-0 sutures for redundancy andsimilar overall total strength are used. Furthermore, the 4-0 sutures101.1 hold the outer reinforcement element 107.6 in place.

When opening and closing the leaflets 102 of the prosthetic heart valve100, the outer reinforcement element 107.6 acts as a bumper to absorbshocks which affect the leaflets 102 during opening. In turn, the innerreinforcement element 107.7 spreads out the compressive forces inducedby the sutures 101.1, thus avoiding stress concentration at thetransition area 104 of the prosthetic heart valve 100.

In the following, reference is made to FIGS. 7a, b for describing afurther exemplary embodiment of a cardiac valve stent capable ofsupporting and anchoring a prosthetic heart valve. In detail, FIG. 7ashows a first perspective side view of a transcatheter deliveredendoprosthesis 1 for treating a narrowed cardiac valve or a cardiacvalve insufficiency, where the endoprosthesis 1 comprises a cardiacvalve stent 10 according to the first exemplary embodiment of the stent(FIGS. 5a-e ) for holding a prosthetic heart valve. FIG. 7b shows asecond perspective side view of the endoprosthesis 1 depicted in FIG. 7a.

In contrast to the exemplary embodiment shown in FIGS. 6a and 6b , theendoprosthesis depicted in FIGS. 7a, b shows the prosthetic heart valve100 according to the second valve embodiment. That is, the prostheticheart valve 100 attached to the stent 10 of FIGS. 7a, b consists ofthree separate pieces 120 being sewn together along their contiguousedges 112. These three separate pieces 120 may either be cut from asingle pericardial sack (xenograft or homograft) or from a plurality ofpericardial sacks.

The endoprosthesis 1 according to the exemplary embodiment illustratedby FIGS. 7a and 7b comprises a stent 10 according to the first stentembodiment depicted by

FIGS. 5a to 5e . This stent 10 comprises a plurality of positioningarches 15 a, 15 b, 15 c configured to be positioned within a pluralityof pockets of the patient's native heart valve and positioned on a firstside of a plurality of native heart valve leaflets, and a plurality ofretaining arches 16 a, 16 b, 16 c configured to be positioned on asecond side of the plurality of native heart valve leaflets opposite thefirst side, wherein furthermore a plurality of leaflet guard arches 50a, 50 b, 50 c are provided, each interspaced between the two arms 15 a′,15 a″, 15 b′, 15 b″, 15 c′, 15 c″ of one of the plurality of positioningarches 15 a, 15 b, 15 c. In addition, the respective arms 16 a′, 16 a″,16 b′, 16 b″, 16 c′, 16 c″ of the retaining arches 16 a, 16 b, 16 c arepreferably provided with a plurality of bending edges 33 in order todivide each arm 16 a′, 16 a″, 16 b′, 16 b″, 16 c′, 16 c″ into aplurality of arm segments, wherein the structure of the stent 10 isprogrammed such that the respective arms 16 a′, 16 a″, 16 b′, 16 b″, 16c′, 16 c″ of the retaining arches 16 a, 16 b, 16 c have a curved shapeat least in the expanded state of the stent 10. In particular, the shapeof the respective arms 16 a′, 16 a″, 16 b′, 16 b″, 16 c′, 16 c″ of theretaining arches 16 a, 16 b, 16 c shall be such defined that the armsfollow the shape of the leaflets 102 of a prosthetic heart valve 100 tobe affixed to the stent 10.

In the structure of the stent 10 according to the embodiment depicted inFIGS. 7a and 7b , one leaflet guard arch 50 a, 50 b, 50 c is provided inbetween each positioning arch 15 a, 15 b, 15 c. Hence, one leaflet guardarch 50 a, 50 b, 50 c is allocated to each positioning arch 15 a, 15 b,15 c.

Each leaflet guard arch 50 a, 50 b, 50 c has a substantially U-shaped orV-shaped structure which is closed to the lower end 2 of the stent 10.In particular, each leaflet guard arch 50 a, 50 b, 50 c has a shape thatis roughly similar to the shape of the positioning arch 15 a, 15 b, 15 cand each leaflet guard arch 50 a, 50 b, 50 c is arranged within the armsof the corresponding positioning arch 15 a, 15 b, 15 c. Furthermore,each of the leaflet guard arches 50 a, 50 b, 50 c extends in the samedirection as the positioning arch 15 a, 15 b, 15 c.

The leaflet guard arches 50 a, 50 b, 50 c are preferably programmed sothat they extend in a radial direction outside the circumference of thestent 10 when the stent 10 is in its expanded state. In this way, anincreased contact force can be applied to the leaflets of the native(diseased) cardiac valve when the stent 10 is in its expanded andimplanted state. This, in turn, allows an increased security in thefixing of the stent 10 in situ.

When the stent 10 is in its expanded and implanted state, the leafletguard arches 50 a, 50 b, 50 c actively keep the diseased leaflets, i.e.the leaflets of the native cardiac valve, from impinging the leaflets102 of a prosthetic heart valve 100 attached to the stent 10, when thepositioning arches 15 a, 15 b, 15 c are placed outside the nativeleaflets. In addition, the leaflet guard arches 50 a, 50 b, 50 c mayalso provide additional anchoring and securing against migration.

An alternative embodiment of a stent 10 is shown in FIGS. 8a-d(hereinafter also named “second stent embodiment”). The stent 10according to the embodiment depicted in FIGS. 8a-d essentially comprisesthe same features as the stent described with reference to FIGS. 5a -e.In particular, the stent 10 also comprises positioning arches 15 a, 15b, 15 c as well as retaining arches 16 a, 16 b, 16 c and an annularcollar 40.

In contrast to the first embodiment of a stent 10 depicted in FIGS. 5a-e, the stent 10 of the second stent embodiment comprises retainingarches 16 a, 16 b, 16 c which are not provided with a number of lowerleaflet attachment regions 11 c, each having a number of additionalfastening holes 12 a or eyelets provided for fastening the tissuecomponents of a prosthetic heart valve 100. Rather, the stent of thesecond stent embodiment is provided with retaining arches 16 a, 16 b, 16c whose arms 16 a′, 16 a″, 16 b′, 16 b″, 16 c′, 16 c″ are segmented by aplurality of bending edges 33 which are not only used for defining abending point of two neighboring arm segments, but also as fasteningnotches which can be used for fixing the prosthetic heart valveprosthesis 100 to the stent 10. It is conceivable, of course, that thefastening notches are adapted to the thickness of the suture, thread orwire. In particular, the additional notches may be radiused to minimizedamage to the suture, thread or wire. Due to the increased number ofbending edges 33 providing fastening notches along the retaining arches16 a, 16 b, 16 c, the retaining arches 16 a, 16 b, 16 c allow for morecontinuous bending along the entire length of their respective arms 16a′, 16 a″, 16 b′, 16 b″, 16 c′, 16 c″, simplifying the attachment ofsaid retaining arches 16 a, 16 b, 16 c to the bendable transition area104 of the prosthetic heart valve 100.

In more detail, FIG. 8a shows a flat roll-out view of a cardiac valvestent 10 pursuant the second embodiment of the stent 10, whereby thestent 10 is in its non-expanded state. This flat roll-out viewcorresponds to a two-dimensional projection of a cutting pattern whichcan be used in the manufacture of the stent 10 pursuant the secondembodiment. This enables a one-piece stent 10 to be cut from a portionof tube, in particular a metal tube.

FIG. 8b shows a first perspective side view of a cardiac valve stent 10according to the second stent embodiment, whereby the cardiac valvestent 10 is shown in its expanded state, and FIG. 8c shows a secondperspective side view the stent 10 according to the second stentembodiment, whereby the cardiac valve stent is also shown in itsexpanded state.

FIG. 8d shows a flat roll-out view of a cardiac valve stent 10 accordingto the second embodiment of the stent. Contrary to the flat roll-outview depicted in FIG. 8a , however, the flat roll-out view according toFIG. 8d shows the cardiac valve stent 10 is in its expanded state.

Thus, the stent 10 according to the second stent embodiment comprises aplurality of positioning arches 15 a, 15 b, 15 c and a plurality ofretaining arches 16 a, 16 b, 16 c. Each of the plurality of positioningarches 15 a, 15 b, 15 c is configured to be positioned within aplurality of pockets of the patient's native heart valve and positionedon a first side of a plurality of native heart valve leaflets. On theother hand, each of the plurality of retaining arches 16 a, 16 b, 16 cis configured to be positioned on a second side of the plurality ofnative heart valve leaflets opposite the first side.

Furthermore, a plurality of leaflet guard arches 50 a, 50 b, 50 c areprovided, each interspaced between the two arms 15 a′, 15 a″, 15 b′, 15b″, 15 c′, 15 c″ of one of the plurality of positioning arches 15 a, 15b, 15 c. In addition, the respective arms 16 a′, 16 a″, 16 b′, 16 b″, 16c′, 16 c″ of the retaining arches 16 a, 16 b, 16 c are preferablyprovided with a plurality of bending edges 33 in order to divide eacharm 16 a′, 16 a″, 16 b′, 16 b″, 16 c′, 16 c″ into a plurality of armsegments, wherein the structure of the stent 10 is programmed such thatthe respective arms 16 a′, 16 a″, 16 b′, 16 b″, 16 c′, 16 c″ of theretaining arches 16 a, 16 b, 16 c have a curved shape at least in theexpanded state of the stent 10. In particular, the shape of therespective arms 16 a′, 16 a″, 16 b′, 16 b″, 16 c′, 16 c″ of theretaining arches 16 a, 16 b, 16 c shall be such defined that the armsfollow the shape of the bendable transition area 104 of the prostheticheart valve 100 to be affixed to the stent 10.

In detail and as depicted in the flat roll-out view shown in FIG. 8a ,the respective arms 16 a′, 16 a″, 16 b′, 16 b″, 16 c′, 16 c″ of theretaining arches 16 a, 16 b, 16 c are provided with a plurality ofbending edges 33. These bending edges 33 may be uniformly distributedalong the length of each retaining arch arm 16 a′, 16 a″, 16 b′, 16 b″,16 c′, 16 c″ thereby dividing each arm 16 a′, 16 a″, 16 b′, 16 b″, 16c′, 16 c″ into a plurality of arm segments. The arm segments of acorresponding retaining arch arm 16 a′, 16 a″, 16 b′, 16 b″, 16 c′, 16c″ are interconnected thereby constituting a retaining arch arm whichdescribes an essentially straight line in the not-expanded state of thestent 10. In this regard, reference is made to the flat roll-out viewdepicted in FIG. 8a which shows the uncurved configuration of therespective arms 16 a′, 16 a″, 16 b′, 16 b″, 16 c′, 16 c″ of theretaining arches 16 a, 16 b, 16 c.

When manufacturing the stent 10, the stent structure and in particularthe structure of the retaining arches 16 a, 16 b, 16 c is programmedsuch that the respective retaining arch arms 16 a′, 16 a″, 16 b′, 16 b″,16 c′, 16 c″ have a curved shape in the expanded state of the stent 10.The shape of the respective retaining arch arms 16 a′, 16 a″, 16 b′, 16b″, 16 c′, 16 c″ is such defined that the arms follow the shape of theleaflets of a prosthetic heart valve 100 to be affixed to the stent 10(cf. FIG. 8d ).

Hence, the respective retaining arch arms 16 a′, 16 a″, 16 b′, 16 b″, 16c′, 16 c″, onto which the prosthetic heart valve 100 is sewn or sewable,will change their shape when the stent 10 expands, wherein the retainingarches 16 a, 16 b, 16 c are curved in the expanded state of the stent10, but relatively straight when the stent 10 is collapsed. Thus, whenin the expanded state, the retaining arches 16 a, 16 b, 16 c of thestent 10 are adapted to fit to the shape of the bendable transition area104 of the prosthetic heart valve 100. In detail, in their expandedstate, the retaining arches 16 a, 16 b, 16 c are adapted to progress inan essentially u-shaped manner, similar to the shape of a natural aorticor pulmonary heart valve, for reducing tissue stresses during theopening and closing motion of the leaflets 102.

As can be seen, for example, in FIG. 8d , the essentially u-shapedcurvature of the respective retaining arch arms 16 a′, 16 a″, 16 b′, 16b″, 16 c′, 16 c″ is achieved by segmenting the arms 16 a′, 16 a″, 16 b′,16 b″, 16 c′, 16 c″. In detail, the arms 16 a′, 16 a″, 16 b′, 16 b″, 16c′, 16 c″ are segmented by providing a plurality of bending edges 33. Inthe expanded state of the stent 10, two neighboring arm segments areangled relative to each other, wherein the bending point of these twoneighboring arm segments is defined by the bending edge 33 which isprovided in between neighboring arm segments. Hence, the greater thenumber of bending edges 33 provided in an arm 16 a′, 16 a″, 16 b′, 16b″, 16 c′, 16 c″ of a retaining arch 16 a, 16 b, 16 c, the greater thenumber of arm segments which may extend in different directions in theexpanded state of the stent 10. In this respect, the shape of therespective retaining arch arms 16 a′, 16 a″, 16 b′, 16 b″, 16 c′, 16 c″can be adapted to the shape of the leaflets 102 of the prosthetic heartvalve 100 to be affixed to the stent 10.

According to the design of the second stent embodiment, the respectivearms 16 a′, 16 a″, 16 b′, 16 b″, 16 c′, 16 c″ of the retaining arches 16a, 16 b, 16 c are not provided with fastening holes 12 a, as it is thecase, for example, in the first embodiment of the stent (FIGS. 5a to 5e). Rather, in the second stent embodiment, the bending edges 33 providedin the retaining arch arms 16 a′, 16 a″, 16 b′, 16 b″, 16 c′, 16 c″ arenot only used for defining a bending point of two neighboring armsegments, but also as fastening notches which can be used for fixing aprosthetic heart valve 100 to the stent 10.

A comparison with, for example, the flat roll-out view pursuant to FIG.5a (first stent embodiment) illustrates directly that the respectiveretaining arch arms 16 a′, 16 a″, 16 b′, 16 b″, 16 c′, 16 c″ of thestent design according to the second stent embodiment is at least partlymuch more thinner compared with the respective retaining arch arms ofthe first stent embodiment which are provided with lower leafletattachment regions having fastening holes 12 a. By reducing the width ofthe retaining arch arms 16 a′, 16 a″, 16 b′, 16 b″, 16 c′, 16 c″, thebendability of the arms is increased which allows a more preciseadaptation of the shape of the respective retaining arch arms 16 a′, 16a″, 16 b′, 16 b″, 16 c′, 16 c″ to the shape of the bendable transitionarea 104 of the prosthetic heart valve 100 to be affixed to the stent10.

Moreover, by using the bending edges 33 provided in the retaining archarms 16 a′, 16 a″, 16 b′, 16 b″, 16 c′, 16 c″ as fastening notches forfixing a heart valve prosthesis to the stent 10, a greater number ofattachment points compared with the number of fastening holes 12 a canbe generated. In this regard, high stress concentrations at each singleattachment point can be effectively avoided. Furthermore, the fasteningnotches provide space and allow for the sutures 101 to be protectedduring collapsing of the valve 100 into the catheter. Therefore,adjacent members of the stent 10 do not impinge on and damage thesutures 101 used to attach the prosthetic heart valve 100 to theretaining arches 16 a, 16 b, 16 c, during collapsing and deployment ofthe prosthetic heart valve 100.

In addition, in the second embodiment of the stent, the attachmentpoints (bending edges 33) to be used for fixing a heart valve prosthesisto the retaining arch arms 16 a′, 16 a″, 16 b′, 16 b″, 16 c′, 16 c″ ofthe stent 10 are more uniformly distributed along the respectiveretaining arch arms 16 a′, 16 a″, 16 b′, 16 b″, 16 c′, 16 c″, therebyproviding a more uniform fixation of a heart valve prosthesis to thestent. Hence, the risk of an axial displacement of the heart valveprosthesis relative to the stent may be further reduced. Each individualbending edge 30 provided in the respective retaining arch arms 16 a′, 16a″, 16 b′, 16 b″, 16 c′, 16 c″ thereby serves to guide a thread or thinwire with which the tissue component(s) of the prosthetic heart valve isaffixed or sewn to the corresponding retaining arch arm 16 a′, 16 a″, 16b′, 16 b″, 16 c′, 16 c″ of the stent 10. In detail, the means (thread orthin wire) provided for fastening the tissue component(s) of theprosthetic heart valve to the respective retaining arch arms 16 a′, 16a″, 16 b′, 16 b″, 16 c′, 16 c″ is guided by way of the bending edge 33acting as fastening notch so that a longitudinal displacement of theprosthetic heart valve relative to the stent 10 is substantiallyminimized. This also allows exact positioning of the prosthetic heartvalve relative the stent 10.

In addition, the stent 10 according to the second stent embodiment mayfurther include at least one auxiliary arch 18 a, 18 b, 18 c interspacedbetween two adjacent retaining arches 16 a, 16 b, 16 c, wherein the atleast one auxiliary arch 18 a, 18 b, 18 c includes a first arm 18 a′, 18b′, 18 c′ connected at a first end thereof to a first retaining arch 16a, 16 b, 16 c and a second arm 18 a″, 18 b″, 18 c″ connected at a firstend thereof to a second retaining arch 16 a, 16 b, 16 c, and wherein thefirst and second arms 18 a′, 18 a″, 18 b′, 18 b″, 18 c′, 18 c″ of the atleast one auxiliary arch 18 a, 18 b, 18 c each include respective secondends connected to an annular collar 40 which is arranged at the lowerend section of the stent body. As in the previously described stentdesign (first stent embodiment), this at least one collar 40 serves asan additional anchoring measure for a stent cut from a portion of a tubeby using the cutting pattern depicted in FIG. 8 a.

In detail, the respective first and second arms 18 a′, 18 a″, 18 b′, 18b″, 18 c′, 18 c″ of the at least one auxiliary arch 18 a, 18 b, 18 c arepart of a strut or web structure which is provided between the first andsecond arms 18 a′, 18 a″, 18 b′, 18 b″, 18 c′, 18 c″ of two adjacentauxiliary arches 18 a, 18 b, 18 c in order to support the prostheticheart valve 100 to be affixed to the stent 10 (see, for example, FIGS.11a and 11 b). As can be seen, for example, from FIG. 8d the strut orweb structure may be composed by a plurality of struts or strut-likemembers which are interconnected such as to form a reinforcementstructure. Each strut or strut-like element of the reinforcementstructure serves as reinforcement member in order to increase thestrength or resistance to deformation of the area between the first andsecond arms 18 a′, 18 a″, 18 b′, 18 b″, 18 c′, 18 c″ of two adjacentauxiliary arches 18 a, 18 b, 18 c. The reinforcement structure therebyprovides mechanical reinforcement to the stent 10. Moreover, thereinforcement members of the reinforcement structure between the firstand second arms 18 a′, 18 a″, 18 b′, 18 b″, 18 c′, 18 c″ of two adjacentauxiliary arches 18 a, 18 b, 18 c provides for an additional support forthe skirt portion 103 of a prosthetic heart valve 100 to be attached tothe stent 10. In fact, it is conceivable to attach the skirt portion 103of a prosthetic heart valve 100 directly to the auxiliary arches 18 a,18 b, 18 c by means of sutures, threads or thin wires, as will beexplained in more detail with reference to FIGS. 11a and 11b below.

The terms “strength” or “resistance to deformation” as used herein maybe used to denote any of a number of different properties associatedwith the reinforcement members. For example, the terms may be used torefer to properties of the material from which the reinforcement membersare made, such as the yield strength, the modulus of elasticity, themodulus of rigidity, or the elongation percentage.

Similarly, the terms may be used to refer to the hardness of thereinforcement members. Hardness may be characterized as the “durometer”of the material, in reference to the apparatus used to measure thehardness of the material. The terms may also be used to denote geometriccharacteristics of the reinforcement members, such as the thickness ofthe reinforcement members. The terms “strength” or “resistance todeformation” may also be used to characterize any combination of theabove properties as well as additional properties and/orcharacteristics.

The strength or resistance to deformation of the area between the firstand second arms 18 a′, 18 a″, 18 b′, 18 b″, 18 c′, 18 c″ of two adjacentauxiliary arches 18 a, 18 b, 18 c can be increased in any number ofways. As can be seen from FIG. 8d , the strength or resistance todeformation of the area between the first and second arms 18 a′, 18 a″,18 b′, 18 b″, 18 c′, 18 c″ of two adjacent auxiliary arches 18 a, 18 b,18 c can be increased, for example, by providing a reinforcementstructure formed by at least one, and preferably by a plurality ofreinforcement elements (e.g. struts or strut-like members) which areinterconnected to each other.

It is also conceivable that a reinforcement web is provided in order toincrease the strength or resistance to deformation of the area betweenthe first and second arms 18 a′, 18 a″, 18 b′, 18 b″, 18 c′, 18 c″ oftwo adjacent auxiliary arches 18 a, 18 b, 18 c. This reinforcement webmay also be composed by a plurality of reinforcement elements (e.g.struts or strut-like members) which are interconnected to each otherthereby forming a rhomboidal pattern.

The strength or resistance to deformation of the area between the firstand second arms 18 a′, 18 a″, 18 b′, 18 b″, 18 c′, 18 c″ of two adjacentauxiliary arches 18 a, 18 b, 18 c can be increased, for example, byincreasing the thickness of the reinforcement members, by eliminatingstress concentration risers in the design of the stent 10, or bychanging other aspects of the geometry of the reinforcement members. Thestrength can also be increased by changing the material properties ofthe stent 10 and/or the reinforcement members. For example, thereinforcement members can be made from a number of different materials,preferably shape memory materials, each having a different level ofhardness. In this regard, it is conceivable to vary the stoichiometriccomposition of the material used for forming the stent and thereinforcement members such as to adapt the material properties of thestent 10 and/or the reinforcement members to the specific needs of eachstent application. It is also conceivable to use different materials,for example nitinol and a shape-memory polymer, for forming the stentand the reinforcement members. In this manner, the selection of thereinforcement members can be tailored to the specific needs of eachstent application. For example, in regions where a high external forceis expected, reinforcement members having a high hardness may bepreferred. The strength may also be increased by combining materialproperties with geometric changes.

As can be seen from FIG. 8d , the stent 10 according to the second stentembodiment is provided with a reinforcement structure which isconstituted by a plurality of lattice cells 70 formed by a plurality ofstruts in the area between the arms 16 a′, 16 a″, 16 b′, 16 b″, 16 c′,16 c″ of two neighbouring (adjacent) retaining arches 16 a, 16 b, 16 c,thereby providing for an additional support for the bendable transitionarea 104 of a prosthetic heart valve 100 to be attached to the stent 10.

In addition, this structure of the lattice cells 70 formed by aplurality of struts in the area between the adjacent arms of twoneighbouring retaining arches 16 a, 16 b, 16 c may provide uniform stentstructure which may minimize blood leakage in the implanted stage of thestent 10 having a heart valve prosthesis attached thereto.

The upper end sections of the respective struts which are forming thestructure of the lattice cells 70 are connected to the respective armsof the retaining arches 16 a, 16 b, 16 c. Preferably, the upper endsections of the struts comprise a widened diameter in order tostrengthen the connection between the upper end sections of the strutsand the arms of the retaining arches 16 a, 16 b, 16 c.

The already mentioned annular collar 40, which is provided at the lowerend section of the stent body, is connected with the stent body via theretaining arches 16 a, 16 b, 16 c on the one hand and the second ends ofthe respective arms 18 a′, 18 a″, 18 b′, 18 b″, 18 c′, 18 c″ of the atleast one auxiliary arch 18 a, 18 b, 18 c on the other hand, whereinthese arms 18 a′, 18 a″, 18 b′, 18 b″, 18 c′, 18 c″ of the at least oneauxiliary arch 18 a, 18 b, 18 c are part of the structure of the latticecells 70. In particular, the stent 10 according to the second embodimentis provided with an annular collar 40 which is shortened in its lengthby having only a single row of cells.

As can be seen from the flat roll-out view pursuant to FIG. 8a , theannular collar 40 at the lower end section of the stent body exhibits aplurality of supporting webs 41 which run parallel to the longitudinalaxis L of the stent 10 in the non-expanded state of the stent 10 and areinter-connected by transversal webs 42. As can be seen from thetwo-dimensional roll-out view pursuant to FIG. 8c , however, in theexpanded state of the stent 10, the supporting webs 41 and thetransversal webs 42 forms a rhomboidal or serpentine-like annular collar40 which abuts against the vascular wall in the implanted state of thestent 10.

In order to further improve securing of the position of an implanted andexpanded endoprosthesis 1 and preventing antegrade migration, the stent10 according to the second stent embodiment is provided with a flared ortapered section with a radius shape at its lower end section 2. Indetail and as depicted in FIGS. 8b and 8c , in the expanded state of thestent 10, the lower end section of the annular collar 40 constitutes theflared or tapered section of the stent 10. As has been described before,the prosthetic heart valve 100 according to the present disclosure, maycomprise a flared or tapered lower end section so as to fit to thedescribed stent shapes.

The stent 10 depicted in FIGS. 8b and 8c has at its lower end section 2a flared or tapered section with a radius shape; however, it is alsoconceivable that the flared or tapered section is not uniformly aroundthe circumference of the stent 10. For example, the stent 10 may have aflare only near the locations of the positioning arches 15 a, 15 b, 15c, wherein no flare is provided near the commissure regions, i.e. theregions in between the two arms 15 a′, 15 a″, 15 b′, 15 b″, 15 c′, 15 c″of two neighboring positioning arches 15 a, 15 b, 15 c.

As depicted in FIGS. 8b and 8c , the stent 10 according to the secondstent embodiment comprises a continuous design of its lower end section2. Due to this continuous design, in the implanted and expanded state ofthe stent 10, via the lower end section 2 of the stent 10 an uniformradial force is applied to the wall of the blood vessel into which thestent 10 is deployed.

If the implanted and expanded stent together with a prosthetic heartvalve affixed thereto extend too far below the annulus of the heart,there may be the risk that the implanted endoprosthesis consisting ofthe stent 10 on the one hand and the prosthetic heart valve 100 on theother hand contacts the nerve bundles and heart block. The nerve bundlesmay enter at a location approximately 6 to 10 mm below the annulus ofthe heart.

In order to avoid the lower end section 2 of the implanted stent 10touching the atrioventricular node, the stent 10 pursuant to the secondstent embodiment is provided with an annular collar 40 which isshortened in its length by having only a single row of cells. In thisregard, the total height of the stent 10 and thus the total height ofthe endoprosthesis 1 to be implanted into the body of the patient arereduced.

Moreover, in the programming process during which the shape of thedesired (expanded) stent structure is fixed, the supporting webs 41 ofthe annular collar 40 may be programmed so that—when the stent 10 of thesecond embodiment is in its expanded state—only the upper section of theannular collar 40 extends in a radial direction outside thecircumference of the stent 10, whereas the lower end section of theannular collar 40 bended relative to the upper section of the annularcollar 40 in the radial direction inside the circumference of the stent10. The lower end section of the annular collar 40 may be bent such thatit extends, for example, approximately parallel to the longitudinaldirection L of the stent 10. In this way, an increased contact force(radial force) is applied by the upper section of the annular collar 40to the wall of the blood vessel into which the stent 10 is deployed,whereas the risk is reduced that the lower end section of the annularcollar 40 can touch the atrioventricular node.

It is important to note, that the stent 10 according to the second stentembodiment comprises a number of notches 12 e uniformly distributedaround the lower end section of the annular collar 40. These notches 12e can be used for fixing a heart valve prosthesis (not shown in FIGS. 8band 8c ) to the stent 10, which may reduce the risk of an axialdisplacement of the heart valve prosthesis 100 relative to the stent 10.Since a plurality of notches 12 e are used as additional fastening meansit is possible to utilize the lower end sections of every supporting web41 of the annular collar 40 for additionally fastening a heart valveprosthesis to the stent 10. This appears directly from the flat roll-outview pursuant to FIG. 8 a.

A comparison with, for example, the flat roll-out view pursuant to FIG.5a (first stent embodiment) illustrates directly that the provision ofeyelets 12 f at the lower end sections of every supporting web 41 of theannular collar 40 requires much more material for each eyelet 12 fcompared with the amount of material which is necessary for formingrespective notches 12 e. Since it is conceivable for the stent 10 toexhibit a structure integrally cut from a portion of tube, in particularfrom a metal tube, which incorporates all structural components of thestent 10, in particular the positioning arches 15 a, 15 b, 15 c, theretaining arches 16 a, 16 b, 16 c and the annular collar 40 with definedadditional fastening means at the lower end thereof, an elaboratecutting pattern for forming the design of the stent 10 from the originaltube portion is important. In particular, it must be taken into accountthat the structure of the stent 10 with all structural stent componentsmust be cut from the limited lateral area of the original tube portion.

Hence, by providing notches 12 e instead of eyelets 12 f as additionalfastening means at the lower end section of the annular collar 40, agreater number of notches 12 e compared with the number of eyelets 12 fcan be generated. In detail, according to the second stent embodiment,the lower end sections of every supporting web 41 of the annular collar40 is provided with a corresponding notch 12 e acting as additionalfastening means. In contrast, in the first embodiment of the stent(FIGS. 5a to 5e ) only the lower end sections of every second supportingweb 41 of the annular collar 40 can be provided with a correspondingeyelet 12 f acting as additional fastening means.

In this regard, the stent design according to the second stentembodiment differs from the first stent design in that at the lower endsection of every supporting web 41 of the annular collar 40 anadditional fastening means is provided. This is due to the fact that, inthe second embodiment of the stent 10, notches 12 e are used asadditional fastening means.

Hence, in the second stent embodiment, the additional fastening means tobe used for fixing a heart valve prosthesis to the stent 10 are moreuniformly distributed around the lower end section of the annular collar40, thereby providing a more uniform fixation of a prosthetic heartvalve to the stent. Hence, the risk of an axial displacement of theheart valve prosthesis relative to the stent may be further reduced.Each individual notch 12 e provided at the lower end section of theannular collar 40 thereby serves to guide a thread or thin wire withwhich the tissue component(s) of the prosthetic heart valve is affixedor sewn to the lower end section of the annular collar 40 of the stent10. In detail, the means (thread or thin wire) provided for fasteningthe tissue component(s) of the prosthetic heart valve 100 to the lowerend section of the annular collar 40 is guided by way of the notches 12e so that a longitudinal displacement of the prosthetic heart valverelative to the stent 10 is substantially minimized. This also allowspositioning of the prosthetic heart valve relative the stent 10. To thisend, as can be seen in FIG. 1, the prosthetic heart valve 100 mayfurther comprise an essentially zig-zag shaped pattern at a lower endsection.

Moreover, by using corresponding notches 12 e for the secure and definedfixing of the tissue component(s) of the prosthetic heart valve to thelower end section of the annular collar 40 of the stent 10, the means(threads or thin wires) used to fasten the tissue component(s) to thestent 10 are effectively prevented from being squeezed and thus degradedwhen the stent 10 with the prosthetic heart valve affixed thereto, i.e.the endoprosthesis 1, is compressed and brought into its collapsed shapesuch as to be ready for being inserted into a catheter system which isused for implanting the endoprosthesis 1. In this regard, the risk ofstructural deterioration in the threads or thin wires used to fasten thetissue component(s) of the prosthetic heart valve 100 to the stent 10 isreduced.

The cross-sectional shape of the notches 12 e may be adapted to thecross-sectional shape of the thread or thin wire used to fasten thetissue component(s) of the prosthetic heart valve 100. This allowsfixing of the tissue component(s) of the prosthetic heart valve 100 tothe stent 10 at a precise predefined position relative to the stent 10.Because the fastening holes 12 are adapted to the thickness and/or thecross-sectional shape of the thread or thin wire used to affix theprosthetic heart valve 100 to the stent 10, relative movement betweenthe stent 10 and the tissue component(s) of the prosthetic heart valve100 due to the peristaltic motion of the heart can be effectivelyprevented when the endoprosthesis 1 is implanted. In the fully expandedand implanted state of the endoprosthesis 1, the tissue component(s) ofthe prosthetic heart valve 100 is/are thus fastened to the stent 10 withminimal play, based on which friction-induced wear of the thread or thinwire used to affix the prosthetic heart valve is minimized. As shown in,for example, in FIG. 8a , the notches 12 e have a semi-circularcross-sectional shape.

As can be seen, in particular from FIGS. 8b to 8d , the stent 10according to the second stent embodiment of the invention may furthercomprise at least one radial arch 32 a, 32 b, 32 c which enables aparticularly secure anchoring of the stent 10 in the site ofimplantation in the heart and which is substantially circumferentiallyaligned with at least one of the plurality of positioning arches 15 a,15 b, 15 c. In addition to its radial arches 32 a, 32 b, 32 c, the stent10 is further provided with a total of three leaflet guard arches 50 a,50 b, 50 c, each comprising two leaflet guard arms. It can be seen fromthe flat roll-out view shown in FIG. 8a that, in the structure of thestent according to the second stent embodiment, a leaflet guard arch 50a, 50 b, 50 c is provided in between each positioning arch 15 a, 15 b,15 c. Hence, in the stent according to the second stent embodiment, aleaflet guard arch 50 a, 50 b, 50 c is allocated to each positioningarch 15 a, 15 b, 15 c.

Referring to the flat roll-out view shown in FIG. 8a , the radial arches32 a, 32 b, 32 c of the stent 10 according to the second stentembodiment extend from the leaflet guard arches 50 a, 50 b, 50 c towardsthe upper end 3 of the stent 10. As is shown most clearly in FIG. 8a ,the stent 10 has three radial arches 32 a, 32 b, 32 c, with each arch 32a, 32 b, 32 c located between the two arms of each leaflet guard arch 50a, 50 b, 50 c. Each radial arch 32 a, 32 b, 32 c has a shape that isroughly inverse to each positioning arch 15 a, 15 b, 15 c and extends inthe opposite direction to each one of the positioning arches 15 a, 15 b,15 c.

On the other hand, each leaflet guard arch 50 a, 50 b, 50 c has asubstantially U-shaped or V-shaped structure which is closed to thelower end 2 of stent. Again, each leaflet guard arch 50 a, 50 b, 50 chas a shape that is roughly similar to the shape of the positioning arch15 a, 15 b, 15 c in between the corresponding leaflet guard arch 50 a,50 b, 50 c is arranged. Furthermore, each leaflet guard arch 50 a, 50 b,50 c extends in the same direction as the positioning arch 15 a, 15 b,15 c.

In the stent design of the second stent embodiment, each arm of aleaflet guard arch 50 a, 50 b, 50 c merges at about the mid-point of thelength of an arm of a radial arch 32 a, 32 b, 32 c into the arm of anopposing radial arch 32 a, 32 b, 32 c. According to the stent design ofthe second stent embodiment, the leaflet guard arches 50 a, 50 b, 50 cproject in the longitudinal direction L of the stent and have a reducedlength such that the positioning arches 15 a, 15 b, 15 c can deployduring the expansion of the stent 10 and the leaflet guard arches 50 a,50 b, 50 c do not interfere during deployment.

The positioning arches 15 a, 15 b, 15 c disposed on the stent 10 andalso the retaining arches 16 a, 16 b, 16 c may be curved in convex andarched fashion in the direction to the lower end section of the stent;i.e. toward the lower end 2 of the stent, whereby such a rounded formmay reduce injuries to the artery as well as facilitate the unfoldingduring the self-expansion. Such a design may enable an easier insertionof the positioning arches 15 a, 15 b, 15 c into the pockets of thenative cardiac valve without correspondingly injuring the neighbouringtissue or blood vessels.

Although not explicitly illustrated in the flat roll-out view accordingto FIG. 8a , in the programming process during which the shape of thedesired (expanded) stent structure is fixed, the leaflet guard arches 50a, 50 b, 50 c are preferably programmed so that they extend in a radialdirection outside the circumference of the stent 10 when the stent 10 ofthe second stent embodiment is in its expanded state. In this way, anincreased contact force can be applied to the leaflets of the native(diseased) cardiac valve when the stent of the second stent embodimentis in its expanded and implanted state. This, in turn, allows anincreased security in the fixing of the stent in situ.

When the stent is in its expanded and implanted state, the leaflet guardarches 50 a, 50 b, 50 c actively keep the diseased leaflets, i.e. theleaflets of the native cardiac valve, from impinging the leaflet tissueof the prosthetic heart valve 100 attached to the stent 10, when thepositioning arches 15 a, 15 b, 15 c are placed outside the nativeleaflets. In addition, the leaflet guard arches 50 a, 50 b, 50 c mayalso provide additional anchoring and securing against migration. Thisfeature may be unique compared to the cage known from the prior artstent designs which are not provided with positioning arches to push thediseased leaflets out of the way.

As can be seen from the roll-out view depicted in FIG. 8a , according tothe stent design of the second stent embodiment, the two arms 32′, 32″of each radial arch 32 a, 32 b, 32 c are connected together at the upperend 3 of the stent 10 by means of a radiused connecting portion or head.This head is not only radiused but also widens at the tip so that thehead abuts against the interior wall of the vessel over as large acontact area as possible when the stent 10 is in its expanded andimplanted state. The heads of each radial arch 32 a, 32 b, 32 c may alsoserve as additional means by which the stent 10 may be retained in acatheter before and during implantation and/or to recapture the stentafter implantation.

In the programming process during which the shape of the desired(expanded) stent structure is fixed, the radial arches 32 a, 32 b, 32 care programmed so that they extend in a radial direction outside thecircumference of the stent 10 when the stent 10 is in its expandedstate. In this way an increased contact force can be applied to thevessel wall by the upper end region of the stent 10. This, in turn,allows an increased security in the fixing of the stent 10 in situ,thereby reducing the likelihood of migration of the stent 10. Therefore,in its expanded state, in addition to the clamping effect of thepositioning arches 15 a, 15 b, 15 c and in addition to the additionalanchoring obtainable by the leaflet guard arches 50 a, 50 b, 50 c, thestent 10 of the second stent embodiment is secured in place onimplantation via radial forces exerted by the retaining arches 16 a, 16b, 16 c, the auxiliary arches 18 a, 18 b, 18 c, the radial arches 32 a,32 b, 32 c, and the annular collar 40, all of which project outwards ina radial direction from the circumference of the stent 10.

It can be seen from the flat roll-out view shown in FIG. 8a that theradial arches 32 a, 32 b, 32 c do not project in the longitudinaldirection L of the stent 10 beyond the plane in which the catheterretaining means 23 or the fastening means with fastening eyelets 24 aresituated. This may ensure that the catheter retaining means 23 canco-operate with corresponding means within a suitable implantationcatheter without interference from the heads of the radial arches 32 a,32 b, 32 c. Indeed, as explained above, the heads themselves can be usedas additional catheter retaining means or additional means to effectexplanation of the stent 10.

In principle, the stent 10 may have more than three radial arches 32 inorder to increase the radial contact force further. It is also possibleto provide barb elements on all or some of the radial arches 32 a, 32 b,32 c, for example, to allow a still better anchoring of the stent 10 atthe implantation site.

Moreover, with respect to fixing the upper area 3 of stent 10 to thewall of the blood vessel into which the stent 10 is deployed, it wouldbe conceivable for the stent 10 to comprise barb members arranged, forexample, on the eyelets 24, the tips of the barbs pointing toward thelower end 2 of stent 10.

In addition, a liner or sheath, typically a fabric, polymeric orpericardial sheet, membrane, or the like, may be provided over at leasta portion of the exterior of the stent 10 to cover all or most of thesurface of the outside of the stent 10, extending from a location nearthe lower end section of the stent to a location near the upper endsection of the stent. The liner may be attached to the stent 10 at atleast one end, as well as at a plurality of locations between said endsthereby forming an exterior coverage. Such exterior coverage provides acircumferential seal against the inner wall of the blood vessel lumen inorder to inhibit leakage of blood flow between the stent 10 and theluminal wall thereby and to prevent a blood flow bypassing theendoprosthesis 1.

For example, the liner may be stitched or otherwise secured to the stent10 along a plurality of circumferentially spaced-apart axial lines. Suchattachment permits the liner to fold along a plurality of axial foldlines when the stent 10 is radially compressed. The liner will furtherbe able to open and conform to the luminal wall of the tubular frame asthe frame expands. Alternatively, the liner may heat welded, orultrasonically welded to the stent 10. The liner may be secured to theplurality of independent arches (positioning arches 15 a, 15 b, 15 c,retaining arches 16 a, 16 b, 16 c, auxiliary arches 18 a, 18 b, 18 c,leaflet guard arches 50 a, 50 b, 50 c) preferably along axial lines. Inaddition, the liner may be secured to the annular collar 40 provided atthe lower end section 2 of the stent 10. The liner will preferably becircumferentially sealed against the stent 10 at at least one end.

By covering at least a part of the outside surface of the stent 10 withthe liner or sheath, thrombogenicity of the endoprosthesis 1 resultingfrom exposed stent elements is greatly reduced or eliminated. Suchreduction of thrombogenicity is achieved while maintaining the benefitsof having a stent structure which is used for spreading up a prostheticheart valve 100 and for anchoring the prosthetic heart valve 100 inplace.

As already mentioned, the stent 10 can be compressed from a relaxed,large diameter configuration to a small diameter configuration tofacilitate introduction. It is necessary, of course, that the outerliner remain attached to the stent 10 both in its radially compressedconfiguration and in its expanded, relaxed configuration.

The liner is composed of pericardial material or conventional biologicalgraft materials, such as polyesters, polytetrafluoroethylenes (PTFE's),polyurethanes, and the like, usually being in the form of woven fabrics,non-woven fabrics, polymeric sheets, membranes, and the like. Apresently preferred fabric liner material is a plain woven polyester,such as Dacron® yarn (Dupont, Wilmington, Del.).

A third embodiment of the stent 10 according to the present invention isdescribed in the following with reference to FIG. 9 which is a flatroll-out view of this embodiment, whereby the cardiac valve stent 10 isshown in its expanded state.

The third embodiment of the stent 10 is similar in structure andfunction with respect to the second embodiment. To avoid repetition,reference is therefore made to the above description of the secondembodiment. In particular, the lower end section of the stent 10 isconstituted by an annular collar 40 which is likewise provided withnotches 12 e acting as additional fastening means.

In addition, the stent 10 according to the third stent embodiment isprovided with retaining arches 16 a, 16 b, 16 c whose arms 16 a′, 16 a″,16 b′, 16 b″, 16 c′, 16 c″ are segmented by a plurality of bending edges33 which are not only used for defining a bending point of twoneighboring arm segments, but also as fastening notches which can beused for fixing a heart valve prosthesis 100 to the stent 10. In turn,the retaining arches 16 a, 16 b, 16 c of the third stent embodiment areadapted to extend along the bendable transition area 104 of theprosthetic heart valve, when the endoprosthesis is assembled.

The third embodiment of the stent 10 also includes radial arches 32 a,32 b, 32 c extending from the positioning arches 15 a, 15 b, 15 ctowards the upper end 3 of the stent 10. As is shown in the FIG. 9, thestent 10 has three radial arches 32 a, 32 b, 32 c, with each arch 32 a,32 b, 32 c located between the two arms 15 a, 15 a′, 15 b, 15 b′, 15 c,15 c′ of each positioning arch 15 a, 15 b, 15 c. Each radial arch 32 a,32 b, 32 c has a shape that is roughly inverse to each positioning arch15 a, 15 b, 15 c and extends in the opposite direction to each one ofthe positioning arches 15 a, 15 b, 15 c.

Contrary to the stent design of the second stent embodiment, however,the stent design of the third embodiment is not provided with leafletguard arches 50 a, 50 b, 50 c. Furthermore, each arm of a radial arch 32a, 32 b, 32 c merges at about the mid-point of the length of the stent10 into an arm 15 a′, 15 a″, 15 b′, 15 b″, 15 c′, 15 c″ of an opposingpositioning arch 15 a, 15 b, 15 c.

A fourth embodiment of the stent 10 according to the present inventionis described in the following with reference to FIG. 10. In detail, FIG.10 is a flat roll-out view of the fourth stent embodiment, whereby thecardiac valve stent 10 is shown in its expanded state.

From a comparison of FIG. 10 with FIG. 8d it is derivable that thefourth embodiment of the stent 10 is similar in structure and functionwith respect to the second embodiment. To avoid repetition, reference istherefore made to the above description of the second embodiment.

The fourth embodiment of the stent 10 only differs from the second stentembodiment in that the respective lower end sections of the leafletguard arches 50 a, 50 b, 50 c are removed. In particular, the lower endsections of the leaflet guard arches 50 a, 50 b, 50 c between the pointswhere each arm of a radial arch 32 a, 32 b, 32 c merges is removed.

Another embodiment of an endoprosthesis 1 according to the presentdisclosure is shown by FIGS. 11a to 11c . In detail, this thirdembodiment of an endoprosthesis 1 includes a stent 10 according to thesecond stent embodiment (FIGS. 8a to 8d ) and a prosthetic heart valve100, in accordance with the second heart valve embodiment (FIGS. 3 and4), affixed thereto.

In particular, FIG. 11a shows a first side view of the third embodimentof the endoprosthesis 1. From this first side view, the characteristicU-shape of the retaining arches 16 a, 16 b, 16 c becomes readilyapparent.

As indicated hereinbefore, this U-shape of the respective arms 16 a′, 16a″, 16 b″, 16 b″, 16 c′, 16 c″ of the retaining arches 16 a, 16 b, 16 cis achieved by segmenting the arms 16 a′, 16 a″, 16 b′, 16 b″, 16 c′, 16c″. In detail, the arms 16 a′, 16 a″, 16 b′, 16 b″, 16 c′, 16 c″ aresegmented by providing a plurality of bending edges 33. In the depictedexpanded state of the stent 10, two neighboring arm segments are angledrelative to each other, wherein the bending point of these twoneighboring arm segments is defined by the bending edge 33 which isprovided in between the both neighboring arm segments. Hence, thegreater the number of bending edges 33 provided in an arm 16 a′, 16 a″,16 b′, 16 b″, 16 c′, 16 c″ of a retaining arch 16 a, 16 b, 16 c, thegreater the number of arm segments which may extend in differentdirections in the expanded state of the stent 10. In this respect, theshape of the respective arms 16 a′, 16 a″, 16 b′, 16 b″, 16 c′, 16 c″ ofthe retaining arches 16 a, 16 b, 16 c can be adapted to the shape oftransition area 104 of a prosthetic heart valve 100 to be affixed to thestent 10 adapted so as to fit the retaining arches 16 a, 16 b, 16 c tothe progression of the bendable transition area 104 of the prostheticheart valve 100.

Further to this, FIG. 11a shows the bending edges providing a number offastening notches which are used to fix the bendable transition area 104to stent 10. Thus, in this third endoprosthesis embodiment, there are noadditional fastening holes 12 a needed along the respective arms 16 a′,16 a″, 16 b′, 16 b″, 16 c′, 16 c″ of the retaining arches 16 a, 16 b, 16c. Rather, the sutures 101 are wrapped around the retaining arches 16 a,16 b, 16 c and sewn to the bendable transition area 104, whilst beingheld in place by the fastening notches which extend essentially in thesame direction as the bendable transition area 104 of the prostheticheart valve. That is, the prosthetic heart valve 100 of the presentthird embodiment of the endoprosthesis 1 is more securely attached tothe stent 10 as the fastening notches provide a greater number ofattachment points compared with the number of fastening holes 12 a, usedin the embodiment according to FIGS. 6a and 6b of the presentdisclosure. In this regard, high stress concentrations at each singleattachment point can be effectively avoided.

Another feature which has already been described with reference to thesecond embodiment of the endoprosthesis 1 depicted by FIGS. 7a and 7b ,is the provision of leaflet guard arches 50 a, 50 b, 50 c. To avoidrepetition, reference is therefore made to the above description of thesecond endoprosthesis embodiment depicted by FIGS. 7a and 7 b.

FIG. 11b shows the connection between the skirt portion 103 and theaforementioned plurality of lattice cells 70. This plurality of latticecells 70 formed by a plurality of struts in the area between the arms 16a′, 16 a″, 16 b′, 16 b″, 16 c′, 16 c″ of two neighbouring (adjacent)retaining arches 16 a, 16 b, 16 c, provides for an additional supportfor the bendable transition area 104 of a prosthetic heart valve 100 tobe attached to the stent 10. As depicted by FIG. 11b , the prostheticheart valve 100 may be directly sewn to the lattice cells 70 by means ofsutures 101, threads or thin wires.

As can further be derived from FIG. 11b , the prosthetic heart valve 100according to the third embodiment of the endoprosthesis 1, comprisesthree separate pieces 120 being sewn together at their contiguous edges112. FIG. 11c shows a perspective top view of the third embodiment ofthe endoprosthesis. In detail, FIG. 11c illustrates the attachment ofthe three separate pieces 120 being sewn together in a cylindricalmanner along their contiguous edges 112. After the contiguous edges 112of the separate pieces 120 are aligned and sewn together, the sleeves111 of the separate pieces 120 are turned to the outside and attached tothe commissural attachment region 11 b of the stent 10. A more detaileddescription of this particular attachment method will be described withreference to FIGS. 19a-c and 20.

It should be noted that this third endoprosthesis embodiment is notmeant to be restrictive. Of course, it is also conceivable to attach aone piece prosthetic heart valve, in accordance with the first valveembodiment (FIG. 1) of the present disclosure, to the stent 10 shown inFIGS. 8a to 8 d.

In the figures of this specification, the prosthetic heart valve 100 isgenerally mounted to the inner surface of the stent 10. Of course, it isalso conceivable to mount the prosthetic heart valve 100 to the outersurface of a support stent 10. That is, the skirt portion 102 could bein direct contact with the diseased native heart valve and could beattached to the stent 10 by means of sutures. Mounting the prostheticheart valve 100 to the outer surface of the stent 10 supports the loadtransfer from the leaflet 102 to the stent 10 and reduces the stressconcentration near the attachment regions 11 b, 11 c. This greatlyreduces stresses on the leaflets 102 during closing and consequentlyimproves the durability thereof. Also, it is possible to design thevalve to obtain improved hemodynamics in the case of mounting the skirtportion to the outer surface of the stent. Additionally, the heart valvematerial which is in direct contact with the diseased native heart valveprovides a good interface for sealing against leakage (i.e.,paravalvular leakage), tissue in-growth and attachment.

An alternative second embodiment of a prosthetic heart valve 100 isshown in FIGS. 3 and 4 as well as FIGS. 19a-c and 20.

In particular, FIGS. 3 and 4 illustrate a flat pattern of the prostheticheart valve material, which has an essentially t-shirt like shape.According to this realisation, the prosthetic heart valve 100 is made ofthree separate pieces 120 exhibiting the depicted t-shirt like shape.The three separate pieces 120 are connected to each other at theircontiguous edges 112 by suturing, in order to form the cylindrical orconical shape of the prosthetic heart valve 100. The three separatepieces 120 may be cut from more than one pericardial sack, so as toobtain three pieces 120 having matching characteristics, e.g., tissuethickness and properties. In addition, the bendable transition area 104is implied in the drawing of FIG. 3. That is, that each of the separatepieces 120 is intended to represent one of the three leaflets 102 of theprosthetic heart valve 100, in addition to the transition area 104 andskirt portion 103. FIG. 4 shows a top view of the three separate pieces120 sewn together and attached to a commissure attachment regions 11 bof a stent according to the further exemplary embodiment of thedisclosure.

The steps for the connection of two of the three separate pieces 120 ontheir contiguous edges 112 are depicted in FIGS. 19a -c.

In a first step, the contiguous edges 112 are brought together andsleeves 111 of the separate pieces 120 are turned to the outside, asshown in FIG. 19 a.

A reinforcement element 107.8 may then be attached to the front surfaceof the sleeves 111 by means of sutures 101.1, preferably applying ablanket stitch. At the same time, the continuous edges 112 are sewntogether by means of the same sutures 101.1, again preferably applying ablanket stitch.

In a third step, the reinforced sleeves 111 are turned even further tothe outside, so that they end up being folded rearwards onto the surfaceof the leaflets 102. This rearward folded position is then secured bymeans of lateral sutures 101.2 stitched on the outer surface of thereinforcement element 107.8.

A top view of the three separate pieces 120 sewn together and attachedto the commissure attachment regions 11 b of a stent 10 is illustratedin FIG. 4. As mentioned before, each of the three separated pieces 120represents one of the three leaflets 102 of the prosthetic heart valve100.

A detailed perspective view of the attachment of the prosthetic heartvalve 100 to the commissure attachment regions 11 b of the presentembodiment is shown in FIG. 20. The reinforcement element 107.8 iswrapped around the rearward folded sleeves 111. This rearward foldedposition is held by the lateral suture 101.2 connecting the oppositeends of the reinforcement element 107.8. The material of thereinforcement element 107.8 preferably has much higher suturingretention strength than the heart valve material of the three separatepieces 120.

For this reason, the reinforcement element 107.8 is used to attach theprosthetic heart valve 100 to the commissure attachment regions 11 b ofthe stent 10, by means of suturing 101.1. Thus, stresses due to thesuturing 101.1 between the stent 10 and the prosthetic heart valve 100are mainly introduced into the material of the reinforcement element107.8, avoiding high stress concentrations in the prosthetic heart valve100. Additionally, the intent of this design is to limit the leaflettravel during the opening phase by pinching the commissure area toprevent the leaflets 102 from hitting the stent 10. Also, this assemblymethod displaces the valve commissures inward radially from the stentpost to further limit the leaflets from hitting the stent.

FIG. 21 illustrates an alternative way of attachment of the prostheticheart valve 100 according to FIGS. 3 and 4 of the present disclosure. Indetail, the sleeves 111 of adjacent separate pieces 120 are formed toenclose an inner cushion 107.2. Therefore, in turn, the leaflets 102 aredisplaced from the commissure attachment region 11 b to limit theleaflets 102 form hitting the stent. Furthermore, the sutures 101.1extending through the sleeves 111 and the inner cushion 107.2 are morehidden and the edges of the sleeves 111 are tucked under the innercushion 107.2. Therefore, in this embodiment, the wear of the prostheticheart valve 100, is significantly reduced as the leaflets 102 of theprosthetic heart valve are not in direct contact with knots of thesutures 101.1 or the edges of the sleeves 111 respectively. Of course,it is generally advantageous for any of the described embodiments, toavoid direct contact between the knots of the sutures 101 and theprosthetic heart valve material by means of reinforcement elements107.1-107.8, in order to reduce wear.

The above disclosure is intended to be illustrative and not exhaustive.This description will suggest many variations and alternatives to one ofordinary skill in this art. All these alternatives and variations areintended to be included within the scope of the claims where the term“comprising” means “including, but not limited to”. Those familiar withthe art may recognize other equivalents to the specific embodimentsdescribed herein which equivalents are also intended to be encompassedby the claims.

Further, the particular features presented in the dependent claims canbe combined with each other in other manners within the scope of thedisclosure such that the disclosure should be recognized as alsospecifically directed to other embodiments having any other possiblecombination of the features of the dependent claims. For instance, forpurposes of claim publication, any dependent claim which follows shouldbe taken as alternatively written in a multiple dependent form from allprior claims which possess all antecedents referenced in such dependentclaim if such multiple dependent format is an accepted format within thejurisdiction (e.g. each claim depending directly from claim 1 should bealternatively taken as depending from all previous claims). Injurisdictions where multiple dependent claim formats are restricted, thefollowing dependent claims should each be also taken as alternativelywritten in each singly dependent claim format which creates a dependencyfrom a prior antecedent-possessing claim other than the specific claimlisted in such dependent claim below.

LIST OF REFERENCE NUMERALS

-   1 endoprosthesis-   2 lower end of the stent/endoprosthesis-   3 upper end of the stent/endoprosthesis-   10 cardiac valve stent/stent-   11 b commissure attachment region of the stent-   11 c lower leaflet attachment region of the stent-   12 a, 12 c additional fastening holes-   12 b auxiliary fastening holes-   15 a-15 c positioning arches-   15 a′-15 a″ arms of the first positioning arch-   15 b′-15 b″ arms of the second positioning arch-   15 c′-15 c″ arms of the third positioning arch-   16 a-16 c retaining arches-   16 a′-16 a″ arms of the first retaining arch-   16 b′-16 b″ arms of the second retaining arch-   16 c′-16 c″ arms of the third retaining arch-   17 first connecting web-   17 d upper end of the first connecting web-   17 p lower end of the first connecting web-   20 head portion of the positioning arch-   21 reference marker-   22 connecting portion between the arms of neighbouring positioning    arches-   23 catheter retaining means-   24 eyelet-   25 second connecting web-   30 head portion/connecting portion of the retaining arch-   32 a-32 c radial arches-   33 bending edges in the arms of the retaining arches-   40 annular collar-   41 supporting web-   42 transversal web-   50 a-50 c leaflet guard arches-   70 structure of lattice cells-   100 prosthetic heart valve-   101 thread-   101.1 suture-   101.2 lateral suture-   101.3 surrounding suture-   101.4 clinging suture-   102 leaflet of the prosthetic heart valve-   103 skirt portion-   104 transition area-   105 commissures-   106 fastening holes-   107.1-107.8 reinforcement element-   108 round edge-   109 cavity-   110 slot-   111 sleeves-   112 contiguous edges-   120 separate piece of prosthetic heart valve-   L longitudinal direction of the stent

1-50. (canceled)
 51. A prosthetic heart valve assembly comprising: atleast two pieces of tissue comprising: a distal portion including aleaflet between a first sleeve and a second sleeve; and a proximalportion having a width less than a width of the distal portion; and atleast two reinforcement elements; wherein the first sleeve of each pieceis coupled to the second sleeve of an adjacent piece to form acommissure of the prosthetic heart valve assembly, and an outer surfaceof each commissure is covered by one of the reinforcement elements. 52.The prosthetic heart valve assembly of claim 51, wherein each piece oftissue is a monolithic piece of natural tissue or synthetic tissue. 53.The prosthetic heart valve assembly of claim 51, wherein eachreinforcement element of the at least two reinforcement elements isflexible and comprises a polymer.
 54. The prosthetic heart valveassembly of claim 51, wherein each reinforcement element of the at leasttwo reinforcement elements comprises polytetrafluoroethylene orpolyethylene terephthalate.
 55. The prosthetic heart valve assembly ofclaim 51, wherein each piece of tissue is a monolithic piece ofpericardial tissue that includes the distal portion and the proximalportion and has a thickness ranging from 160 μm to 300 μm.
 56. Theprosthetic heart valve assembly of claim 51, wherein, for eachcommissure, end portions of the first sleeve and the second sleeve arefolded away from each other.
 57. The prosthetic heart valve assembly ofclaim 51, wherein, for each commissure, end portions of the first sleeveand the second sleeve are sutured to a perimeter of the reinforcementelement.
 58. The prosthetic heart valve assembly of claim 51, whereinthe at least two pieces are cut from a single sheet of pericardialtissue.
 59. The prosthetic heart valve assembly of claim 51, wherein theat least two pieces are cut from different sheets of pericardial tissue.60. The prosthetic heart valve assembly of claim 51, wherein theproximal portion of each piece includes a first side edge extending fromthe first sleeve to a proximal zigzag edge and a second side edgeextending from the second sleeve to the proximal zigzag edge, andwherein the first side edge of each piece is sutured to the second sideedge of an adjacent piece.
 61. The prosthetic heart valve assembly ofclaim 51, wherein the prosthetic heart valve assembly is attached to aninner surface of an expandable stent, the at least two reinforcementelements being sutured to respective commissure posts of the stent. 62.The prosthetic heart valve assembly of claim 61, wherein each commissurepost includes two holes distributed along a longitudinal axis of thecommissure post.
 63. The prosthetic heart valve assembly of claim 61,wherein a distal end of each commissure post includes a rounded elementfor attachment to a catheter, each reinforcement element being suturedto a respective commissure post at a location proximal to the roundedelement.
 64. A prosthetic heart valve assembly comprising: at least twopieces of tissue comprising: a distal portion including a leafletbetween a first sleeve and a second sleeve; and a proximal portionincluding a first side edge, a second side edge, and a bottom edge,wherein the first side edge is straight from the first sleeve to thebottom edge, and the second side edge is straight from the second sleeveto the bottom edge; and at least two flexible reinforcement elements;wherein the first sleeve of each piece is coupled to, and folded awayfrom, the second sleeve of an adjacent piece to form a commissure of theprosthetic heart valve assembly.
 65. The prosthetic heart valve assemblyof claim 64, wherein an outermost surface of each commissure is coveredby one of the reinforcement elements, and wherein each reinforcementelement comprises polytetrafluoroethylene or polyethylene terephthalate.66. The prosthetic heart valve assembly of claim 64, wherein each pieceof tissue is a monolithic piece of pericardial tissue, the prostheticheart valve assembly comprising three monolithic pieces sutured togetherto form three commissures, and wherein a proximal end of the prostheticheart valve assembly has a zigzag shape.
 67. A prosthetic heart valveassembly comprising: three pieces of monolithic tissue, each piececomprising: a distal portion including a leaflet between a first sleeveand a second sleeve; and a proximal portion having a first side edge, asecond side edge, and a zigzag edge; and three reinforcement elements;wherein the first sleeve of each piece is coupled to the second sleeveof an adjacent piece to form a commissure of the prosthetic heart valveassembly, and an outer surface of each commissure is covered by one ofthe reinforcement elements.
 68. The prosthetic valve assembly of claim67, wherein a width of the proximal portion of each piece between thefirst side edge and the second side edge is less than a width of thedistal portion between the first sleeve and the second sleeve.
 69. Theprosthetic valve assembly of claim 67, wherein the prosthetic heartvalve assembly is attached to an inner surface of an expandable stent,the three reinforcement elements being sutured to three respectivecommissure posts of the stent.
 70. The prosthetic valve assembly ofclaim 69, wherein a proximal end of the stent includes a row of latticecells, and the zigzag edges of the pieces of tissue are sutured to therow of lattice cells.